If using canned chickpeas and black beans, rinse them well under cold water and drain thoroughly. Spread them on a tray or towel and let them dry for a few minutes. If using dried chickpeas, cook them until tender but not falling apart. Cool completely before using. The beans must be fully drained and fairly dry on the surface. Wet beans dilute the dressing and make the salad watery. That thorough draining and drying is what protects the finished dressing's own concentration — any residual surface moisture would work against it the moment the beans are tossed in.

Dice the tomatoes small. If they are very juicy, remove the seeds and watery pulp first. Finely dice the red onion. Finely chop the parsley and mint. Collect the pomegranate seeds and keep them separate for the final mix. Keep all cuts fairly small and even so the salad eats as a balanced mix, not as large chunks scattered through beans. That consistent, small dice matters directly for how the finished salad actually eats — evenly sized pieces let every bite carry a genuine mix of components rather than landing on one ingredient at a time.

In a large mixing bowl, whisk together the lemon juice, olive oil, garlic, cumin, sumac, salt, and black pepper. Add the sugar or honey only if needed to round the acidity. Taste the dressing. It should be bright, lemony, slightly earthy from cumin, and lightly tangy from sumac. Season the dressing strongly enough before adding the beans. Chickpeas especially need assertive seasoning or the salad will taste flat. That deliberately bold early seasoning accounts for real, predictable dilution once the beans, tomato, and herbs all join — a milder dressing would read as noticeably flat by the time everything is actually combined.

Add the diced red onion to the dressing and let it sit for 10 minutes. This takes the raw harsh edge off the onion and lightly pickles it. This step makes a noticeable difference. Skipping it can leave the onion too aggressive compared with the delicate herbs and beans. That brief soak in the dressing's own acidity genuinely mellows the onion's sharpest, most sulfurous notes, letting it sit comfortably alongside the salad's more delicate components rather than overwhelming them.

Add the chickpeas, black beans, and tomatoes to the bowl with the dressing and onions. Toss gently until evenly coated. Fold in most of the parsley, most of the mint, and most of the pomegranate seeds. Reserve a little of each for finishing. Taste and adjust with more salt, lemon juice, or sumac as needed. Toss gently. Overmixing can break the chickpeas and make the salad cloudy and heavy. That deliberately gentle tossing protects the beans' own distinct, whole shape — vigorous mixing would begin breaking them down, clouding the dressing and working against the salad's whole intended texture.

Transfer to a wide shallow serving bowl. Scatter over the reserved herbs and pomegranate seeds. Dust lightly with extra sumac. Serve immediately, or let it sit for 10–15 minutes at cool room temperature so the beans absorb the dressing. Reserving a final portion of herbs and pomegranate specifically for this finishing stage keeps those elements genuinely vivid and visible right at the surface, rather than buried throughout the tossed salad beneath.