Cook the sweet potatoes. Pierce each potato a few times with a fork. Microwave until tender, 8–10 minutes total, flipping halfway. Or roast at 400°F (200°C) for 45–55 minutes. Let cool until easy to handle, then scoop out the flesh.

Mash and season. In a large bowl, add the sweet potato flesh. Mash until mostly smooth. Stir in tomato paste, lime juice, olive oil, cumin, smoked paprika, chili powder, salt, and pepper.

Prep the beans. Pat the black beans dry with a clean towel. Add them to the bowl and lightly mash about half, leaving some beans whole for texture.

Build the structure. Stir in the onion, garlic, oats, breadcrumbs, and flour. If using, add chopped cilantro or chipotle. The mixture should be soft but not sticky. If it’s too wet, add a bit more oats or breadcrumbs.

Chill to firm up. Cover and chill the mixture for 20–30 minutes. This step helps the patties hold their shape when cooking.

Shape the patties. With lightly oiled hands, form 6 patties about 3/4 inch thick. Press gently to flatten and smooth the edges.

Cook on the stovetop. Heat a large nonstick skillet over medium heat with a light drizzle of oil. Cook patties 4–5 minutes per side until browned and crisp on the outside. Avoid moving them too soon so they develop a crust.

Optional oven finish. For extra firmness, transfer patties to a baking sheet and bake at 375°F (190°C) for 8–10 minutes after searing.

Assemble. Toast buns if you like. Layer with sauce, lettuce, tomato, avocado, and the burger. Add pickled onions or jalapeños for brightness and heat.

Serve. Enjoy immediately with a simple slaw, baked fries, or a green salad.