Place the diced potatoes in a pot of cold salted water. Bring to a boil and cook for 10 to 12 minutes, until fully tender. Drain, reserving some of the cooking water. Mash the potatoes roughly while still warm. They should be mostly mashed but not perfectly smooth. The potato is what binds the filling. If the potato stays in hard cubes, the filling will fall apart inside the empanadas. That specific, rough mash gives the potato genuine structural work to do — enough broken-down starch to physically bind the other ingredients together, while still retaining enough texture to keep the filling from turning into a smooth paste.

Heat the oil in a skillet over medium heat. Add the onion and cook for 4 to 5 minutes, until softened. Add the tomato, garlic, black pepper, cumin, achiote or paprika, and about 5g salt. Cook for 3 to 4 minutes, until the tomato breaks down and the mixture looks thick and saucy. Add the ground beef and cook for 6 to 8 minutes, breaking it up well with a spatula, until browned and cooked through. Stir in the mashed potatoes and cilantro. Add a splash of reserved potato water only if the mixture feels dry. The filling should be soft, cohesive, and spoonable, but not wet. If liquid pools in the pan, cook it down before shaping or the empanadas can burst while frying. That specific, checkable texture — cohesive but genuinely not wet — is directly what protects the masa's own ability to seal cleanly around the filling once shaping begins.

Transfer the filling to a tray or bowl and let it cool until warm or room temperature. Taste and adjust with the remaining salt if needed. Hot filling softens the masa too much and makes the empanadas harder to seal. That cooling period protects the dough from a real, specific risk — masa in direct contact with genuinely hot filling would soften considerably faster than intended, compromising its ability to hold a clean seal during shaping.

In a bowl, mix the cilantro, scallions, chili, garlic, vinegar, lime juice, water, oil, salt, sugar, and tomato if using. Let it sit for at least 15 minutes before serving. The ají should taste sharp, fresh, salty, and lightly spicy. It is supposed to cut through the fried masa, not taste mild or flat. That resting period gives the individual ingredients real time to meld together into one cohesive, sharp condiment, rather than tasting like separate components simply sharing the same bowl.

In a large bowl, mix the warm water, salt, achiote or paprika, and oil. Add the masarepa gradually, mixing with your hand or a spoon until a soft dough forms. Knead gently for 2 to 3 minutes, then cover and rest for 10 minutes. After resting, the dough should feel soft, smooth, and easy to press without cracking. If the dough cracks around the edges when pressed, add warm water 1 tbsp at a time. If it feels sticky and loose, add a little more masarepa. Adding the masarepa gradually while mixing, rather than dumping it in all at once, is what prevents dry lumps from forming — pre-cooked cornmeal hydrates quickly, and lumps that form early tend to persist even through continued mixing.

Divide the masa into 16 equal portions, about 55 to 60g each. Keep the portions covered with a damp towel so they do not dry out. That damp covering protects every unshaped portion from drying and cracking at the edges while you work through the rest, which would otherwise compromise the dough's ability to seal cleanly around the filling.

Place one dough portion between two sheets of plastic wrap or parchment. Press into a round about 12 to 13cm wide. Add about 2 tbsp filling to one side of the dough, leaving a clean edge. Fold the dough over into a half-moon shape. Press the edges firmly to seal, then trim with a bowl or round cutter if you want a cleaner shape. Repeat with the remaining dough and filling. The edge must be fully closed with no filling exposed. Any weak seam can open in the fryer. That thorough, deliberate sealing along the entire edge is what protects each empanada from splitting open the moment it hits the genuinely hot oil, where any weak point would be exposed immediately.

Heat neutral oil in a deep pot to 175°C. Set a wire rack or paper towel-lined tray nearby. 175°C is the target. Cooler oil makes greasy empanadas; hotter oil browns the outside before the shell crisps properly. Maintaining that specific temperature protects the empanadas from both directions at once — too cool lets the masa soak up excess fat before it ever crisps, while too hot darkens the shell well before it's actually developed the proper crisp, craggy texture.

Fry the empanadas in batches for 4 to 5 minutes, turning occasionally, until deep golden-orange, crisp, and lightly blistered. Do not overcrowd the pot. Transfer to the rack and season lightly with a tiny pinch of salt while hot if needed. The shell should look crisp and craggy, not pale and soft. If the color is right but the crust still feels soft, fry 30 to 60 seconds longer. That specific visual and textural check — colour alone isn't enough — protects against pulling the empanadas before the shell has genuinely finished developing its full, characteristic crispness.

Serve the empanadas hot with lime wedges and ají picante on the side. Each serving gets 4 empanadas. Serving while genuinely hot delivers the shell at its crispest — that texture softens steadily the moment the empanadas come off the heat.