In a saucepan over medium heat, warm one teaspoon of olive oil. Add the finely chopped white onion and cook until softened, about 3-4 minutes. Stir in the taco seasoning and cook for an additional 30 seconds.
Add the rinsed and drained black beans (or cooked beans) to the saucepan, along with the water. Season with freshly ground black pepper to taste.
Cook for about 5 minutes, mashing some of the beans with the back of a spoon. Stir in the lime juice and continue to cook for another 2-3 minutes, until thickened. Remove from heat and set aside.
Place each corn tortilla directly on the oven rack and heat them for about 5 minutes or until they are warmed through and slightly crispy on the edges. Keep the warmed tortillas warm by wrapping them in a clean kitchen towel or aluminum foil until ready to assemble the Huevos Rancheros.
In the skillet, heat 1 teaspoon of olive oil over medium heat. Crack each egg into the skillet and cook until the whites are set but the yolks are still runny, about 3-4 minutes. Remove from heat and set aside.
Place a warm tortilla on each plate. Spoon a generous amount of the cooked beans onto each tortilla. Top with a fried egg. Spoon the red salsa over the eggs.
Sprinkle crumbled Cotija or feta cheese over the top, if desired. Add sliced avocado, additional chopped cilantro, and/or hot sauce for extra flavor. Serve immediately, and enjoy this delicious and satisfying dish for breakfast, brunch, or any meal of the day!