Preheat oven to 450°F. Rinse and halve tomatoes. Halve avocados and discard pits. Using a spoon, carefully scoop out flesh, discarding skins. Cut into .5-inch pieces. Place in a medium bowl. Rinse cilantro; roughly chop leaves, discarding stems. Halve 2 limes. Quarter remaining lime. Mince garlic. Peel onion and cut into small dice. Pat steaks dry and rub with half of spice mix, 1 teaspoon salt, and pepper. Set aside.

Add tomatoes, half of cilantro, juice of 2 limes, .5 cup diced onion, 1 tablespoon olive oil, .25 teaspoon salt, and pepper to bowl with avocado, stir to combine, and set aside. Rub 2 baking sheets with 1 tablespoon olive oil each. In a separate medium bowl, combine masa harina and .5 teaspoon salt. Slowly stir in 1.33 cups water until fully incorporated. Using your hands, knead dough until smooth and holds together.

Using your hands, form dough into 8 equal balls, then flatten each to form a smooth disk, about .25-inch thick. Divide doughs between prepared baking sheets. Working 1 at a time, pinch and crimp edges all the way around to form a .5-inch rim (the sopes should resemble small pie dishes). Rub sopes all over with olive oil and bake until lightly browned, 18-20 minutes. Then, remove from oven, sprinkle with salt, and divide among serving plates.

While sopes bake, heat 1 tablespoon olive oil in a small pot over medium heat. When oil is shimmering, add remaining onion. Cook until soft, 5 minutes. Add garlic and remaining spice mix. Cook, stirring, until fragrant, 1 minute. Add beans and .5 cup water. Increase heat to high. Bring to a boil. Reduce heat to medium. Cook, stirring, until thick, 15-17 minutes. Remove from heat. Using a fork, mash until smooth. Stir in .75 teaspoon salt and pepper to combine.

While beans cook, heat 1 tablespoon olive oil in a large pan over medium-high heat. When oil is shimmering, add corn. Cook until lightly browned, 2-3 minutes, then transfer to bowl with salsa. Stir to combine. Heat 2 tablespoons olive oil in pan from corn over medium-high heat. When oil is shimmering, add steaks. Sear until browned and medium rare, 4-5 minutes per side. Transfer steaks to a cutting board. Set aside to rest, about 5 minutes.

Once steaks have rested, cut against the grain into .25-inch slices (see Recipe Tip). Top sopes on serving plates with refried beans, then corn salsa, then steak. Garnish with queso fresco and remaining cilantro and serve with lime wedges for squeezing over. Dig in!