Preheat oven to 375°F (190°C).
In a bowl, combine drained corn, chopped cilantro, lime juice, jalapeno, 2 tablespoons ground cumin, 1 tablespoon onion powder, 1 tablespoon dried oregano, chopped garlic, Himalayan salt, olive oil, and liquid smoke. Mix well to create the corn salsa.
In another bowl, mix the refried black beans with 1 tablespoon ground cumin, 1 tablespoon dried oregano, 1 tablespoon garlic powder, 1 tablespoon onion powder, 1 teaspoon black pepper, and 1/2 teaspoon salt. Stir until well combined and set aside.
Brush the portobello mushroom caps with olive oil and season with 2 teaspoons ground cumin, 2 teaspoons dried oregano, 2 teaspoons garlic powder, 2 teaspoons onion powder, 1 teaspoon black pepper, and 1/2 teaspoon sea salt evenly.
Place the mushrooms on a baking sheet, gill side up, and bake for 12-15 minutes until tender.
Remove mushrooms from oven and fill each mushroom cap first with a spoonful of the spiced refried black beans, then top with the corn salsa mixture.
Sprinkle shredded Cheddar cheese evenly over the filled mushroom caps.
Return to oven and bake for an additional 5-7 minutes, or until cheese is melted and bubbly.
Remove from oven and top each mushroom cup with a spoonful of mashed avocado and diced Roma tomato.
Serve warm as a hearty appetizer or light meal and enjoy the festive blend of flavors.