Slice the polenta in half. Slice each half into six rounds, about 1/2-inch thick, so you have 12 rounds total.
Heat oil in a large nonstick skillet over medium-high heat. Gently slide each polenta round into hot oil using a spatula.
Fry for 5 minutes per side or until golden brown and cooked through. Remove from oil and drain on a paper towel-lined sheet tray.
In a medium bowl, combine beans, salsa, and 2 teaspoons hot taco sauce. Mash beans with a fork.
In a small bowl, combine the sour cream, remaining hot taco sauce, and lime juice and mix until well blended.
Spread 2 tablespoons mashed black beans on top of a fried polenta round.
Top with a pinch of shredded lettuce and about 1 tablespoon of the salsa, and drizzle with some of the sour cream mixture.