I was raised in Missouri, and I can't really think of anything that is special to Missouri. I have looked through some community cookbooks and nothing pops up. It seems there are a lot of recipes that call for a can of soup, but that's not the kind of thing you are looking for, is it?
Here is a recipe for Ozark Pudding. It was supposed to be a favorite of Harry Truman. I think the original called for black walnuts, there used to be a lot of black walnut trees in Missouri before they were cut down for the wood.

OZARK PUDDING

1 egg
3/4 cup sugar
2 Tablespoons flour
1/4 teaspoon baking powder
1/8 teaspoon salt
1/2 cup chopped walnuts
1 cup chopped apples
1 teaspoon vanilla
Beat egg and sugar until smooth and creamy. Combine flour, baking powder, and salt. Mix well and stir into egg mixture. Add nuts, apples and vanilla. Mix gently and put in a 8 x 8 inch baking dish. Bake 350 degrees for 35 minutes. Serve warm with whipped cream or ice cream.