Preheat oven to 350°F. Spray a baking sheet with cooking spray and set aside.
In the basin of a food processor, pulse together the black beans, green pepper, onion, garlic cloves, egg, chili powder, salt, pepper and Sriracha sauce until well-mixed. The mixture will be pretty liquid-y.
Transfer the black bean mixture into a medium mixing bowl, and stir in the breadcrumbs. Form mixture into 12 slider-sized patties and place on prepared baking sheet. Bake in preheated oven for 20 minutes, flipping once halfway through baking. Or until the burgers have begun to dry out and turn golden brown.
While the burgers are in the oven, mix together all the sauce ingredients in a small bowl and set aside.
To assemble sliders, place a leaf of lettuce, one slider patty, some red onion rings and a dollop of the sauce onto each slider bun.