Step 1

Preheat the oven to 350 degrees F.

Step 2

Add butter to a large skillet over medium heat. When the butter has melted, add the onions.

Step 3

Reduce the heat to low and cook the onions for about 30 minutes, stirring occasionally.

Step 4

Place half of the onions in a small casserole dish, which has been greased or sprayed with non-stick cooking spray.

Step 5

Add half the sour cream and spread out evenly.

Step 6

Sprinkle half the Mexican grated cheese evenly over the top.

Step 7

Top with half of the Parmesan cheese and half of the Ritz cracker crumbs.

Step 8

Repeat the layers ending with a layer of Ritz cracker crumbs.

Step 9

Bake uncovered for 25 or 30 minutes or until the mixture is bubbly and the topping is golden brown.