Heat 1 tablespoon olive oil in a skillet over medium-high heat. Add the chopped onion and bell pepper and sauté for 3–4 minutes until tender, then add minced garlic and cook 1 more minute. Remove from heat and let cool 2–4 minutes.
Drain and rinse the black beans, then pat dry with paper towels to remove excess water. Place beans in a large bowl and gently mash with a fork until mostly chunky.
Add the pulsed instant oats, eggs, shredded cheese, sriracha, chili powder, cumin, garlic powder, salt, pepper, and chopped cilantro to the mashed beans. Stir until evenly combined.
Cover the mixture and refrigerate 15–20 minutes to allow the oats (or breadcrumbs) to absorb moisture and firm up.
Divide the chilled mixture into 8 even portions and shape each into a patty.
Stovetop: Heat 1 tablespoon oil in a skillet over medium-high and cook patties 3–4 minutes per side until crispy and set.
Bake: Preheat oven to 375°F (190°C). Place patties on a lined baking sheet and bake 15–20 minutes until cooked through and slightly crispy.
Grill: Place patties on greased foil and grill 7–9 minutes per side until charred and cooked through.
Air fryer: Preheat air fryer to 375°F (190°C) and air fry patties about 15 minutes until crispy and cooked through.
Serve the burgers on buns with spicy mayo or your preferred toppings.