Preheat oven to 425 degrees. Place portabella caps on a baking sheet. Roast for 10-13 minutes, until the mushroom caps are softened.

Drizzle with a tablespoon olive oil, salt and pepper.

In a skillet over medium heat, drizzle tablespoon on olive oil in skillet, cook onion until softened (about 2-3 minutes).

Add lentils, burger grounds, and chili seasoning. Spoon into roasted mushroom caps.

Top with a slice of tomato, salt lightly. Sprinkle with cheese.

Return to oven and bake an additional 6-8 minutes, until the cheese melts and starts to bubble