Soak black beans overnight (optional).

Heat vegetable oil in a medium saucepan over medium-high heat.

Add onion, jalapeno, cilantro, and cumin to the saucepan.

Cook, stirring, until the onions are soft, about 4 minutes.

Add the soaked black beans to the saucepan.

Add water until the beans are covered by 2 inches and bring to a simmer.

Cover and cook, adding water if necessary to keep the beans just covered, until the beans are soft and the liquid has begun to slightly thicken, about 40 minutes.

Season to taste with salt, pepper, and lime juice.

Heat 1/4 inch of oil in a medium saucepan until shimmering.

Add a tortilla and cook until golden and puffed, then flip and continue to cook until both sides are golden.

Transfer the cooked tortilla to a paper towel-lined plate and immediately season with salt.

Repeat with remaining tortillas.

Heat a drizzle of vegetable oil in a large non-stick or cast iron skillet over medium-high heat.

When oil just begins to smoke add as many eggs as your pan will allow without overcrowding.

Fry the eggs until the whites are set and the yolks are runny.

Divide tostadas between 4 plates.

Top each tostada with warm beans, followed by an egg, sliced avocado, cilantro, and scallions.

Serve immediately with sliced lime and hot sauce.