Prepare the salsa fresca by combining diced tomatoes, minced yellow onions, minced jalapenos, lime juice, minced cilantro, olive oil, minced garlic, sea salt, and fresh cracked black pepper. Chill for at least one hour to allow the flavors to meld.

Make the guacamole: Combine avocados, minced yellow onion, minced jalapeno, minced cilantro, minced garlic, lime juice, sea salt, and fresh cracked pepper in an electric mixer and blend until smooth.

Preheat the oven to 250°F (120°C) for toasting the bolillos rolls.

Heat the refried beans over medium-low heat until hot.

Cook the thinly sliced flank steaks in a large skillet or on a barbecue grill until lightly browned on the outside and still slightly pink in the middle.

Let the cooked steaks rest for 5 minutes.

While the meat is resting, slice the bolillos rolls in half and toast them in the preheated oven for about 4 minutes.

Cut the rested carne asada into small pieces or strips.

Spread one half of each bolillos roll with guacamole.

Spread the other half of each bolillos roll with hot refried beans.

If using, sprinkle shredded cheddar cheese on top of the beans.

Top the beans (and cheese, if using) with the sliced carne asada, chopped lettuce, salsa fresca, and hot sauce (if using).

Close the sandwich halves together, press down slightly, and cut each sandwich in half.

Serve immediately with extra salsa and guacamole.