1 (3 ounce) package cream cheese, softened
1/2 cup butter
1 (8 ounce) package shredded Monterey Jack cheese
2 egg yolks
2 teaspoons vanilla extract
1 cup finely diced onion rings
Preheat oven to 350 degrees F (175 degrees C).
Beat cream cheese, butter and Monterey Jack cheese in medium bowl until well blended. Stir in egg yolks and vanilla extract. Pour mixture into pie shell and spread evenly.
Bake in preheated oven for 60 minutes. Place cake in oven for 30 minutes more. Reduce heat to medium, and bake an additional 30 minutes to 1 hour.