Preheat oven to 400°F (200°C). Lightly mist corn tortillas with oil spray and bake on a sheet pan for 4 to 6 minutes per side until crisp and golden.
In a small non-stick skillet over medium heat, sauté onion and jalapeño in olive oil until softened, approximately 4 minutes.
Add minced garlic to the skillet and cook for 60 seconds until fragrant.
Stir in the crushed tomatoes, cumin, and oregano. Simmer the sauce for 5 minutes until slightly thickened, then season with salt and pepper.
In a separate small saucepan, warm the black beans with one tablespoon of water over medium-low heat, mashing a portion of the beans with a fork to create a textured base.
Prepare eggs as desired—sunny-side up or poached are recommended—in a non-stick pan using minimal heat-stable oil or spray.
Assemble by placing two crispy tortillas on each plate and spreading a layer of warm black beans over them.
Top each tortilla with one egg and a generous portion of the warm ranchero sauce.
Garnish with avocado slices, fresh cilantro, and a sprinkle of crumbled cheese. Serve immediately with lime wedges on the side.