Best-Ever Potatoes

Best-Ever Potatoes(well 1 of them,I have Many BEST EVER recipes)

7 cups coarsely chopped small red potatoes
1 cup chopped onion
1 8-ounce carton dairy sour cream
1 cup (4 oz.) shredded Monterey Jack cheese
1 cup (4 oz.) shredded sharp cheddar cheese
1/2 teaspoon salt
1/4 to 1/2 teaspoon ground red pepper
2 medium tomatoes, seeded and chopped

In a large saucepan cook potatoes and chopped onion, covered, in a small amount of boiling water for 12 to 15 minutes or until tender; drain. Stir in sour cream, Monterey Jack cheese, cheddar cheese, salt, and red pepper. Stir in chopped tomatoes. Spoon into a 2-quart rectangular baking dish. Bake, uncovered, in a 350F oven about 30 minutes or until heated through