Step 1

Preheat oven to 400 degrees F.

Step 2

Combine 2 tablespoons oil, 1/2 teaspoon garlic powder, 1/8 teaspoon salt and pepper in a small bowl. Using a silicone brush, coat mushrooms all over with the oil mixture. Place the mushrooms on a large rimmed baking sheet and bake until mostly soft, about 10 minutes.

Step 3

Meanwhile, heat the remaining 1 tablespoon oil in a medium saucepan over medium-high heat. Add onion; cook, stirring, until almost soft, about 3 minutes. Add cumin and the remaining 1/2 teaspoon garlic powder and 1/4 teaspoon salt; stir until incorporated. Add corn and beans; cook, stirring, until hot. Remove from heat and stir in cilantro and cheese. Divide the mixture between the mushrooms and bake until the cheese is melted and the filling is heated through, 5 to 7 minutes. Serve with pico de gallo, if desired.