Saute onion and garlic over medium heat until golden, tender and fragrant. Add the spices and salt, and saute 1 minute.
Add the drained black beans, zest and lime juice. Stir well, then mash with a potato masher until mostly mashed, leaving a little texture, then stir until combined. (You could also pulse in a food processor). Taste, adjust heat level.
At this point you can add ¼-⅓ cup ground flaxseed if you want this vegan. Otherwise, let cool, add the egg, cilantro, scallions and the bread crumbs and mix well until combined well. Let stand 10-15 minutes so the breadcrumbs or/flax have a chance to absorb moisture.
Using clean damp hands, form and compress tightly into 4 large patties (or 5 or 6 smaller ones), smoothing the edges. If the mixture seems too soft either refrigerate to firm up, for 30 minutes, or add more bread crumbs/flax.
Heat 1 tablespoon oil in a skillet, over medium heat. Sear each side 5-7 minutes, or until golden and heated all the way through (you want the egg to cook though). Place in a warm oven until ready to serve – and feel free to top with melty cheese.
Refrigerate or freeze the seared black bean burgers for later use ( let cool, then wrap tightly in plastic wrap).
To reheat, warm in an oven, toaster oven or on the grill. (Great for making ahead)
Serve on toasted buns, with chipotle mayo, Mexican slaw or Curtido and avocado if you like, or over a bed of dressed greens and/ and grains with fresh veggies!