Preheat oven to 350ºF. Grease bottom and sides of a 9 x 2 inch springform pan or 9 x 1 1/2 inch round pan with shortening.
In a medium bowl, add sugar, butter and egg. With an electric mixer on low speed, beat mixture about 30 seconds or until smooth. Blend in Bisquick and spread over bottom and up one inch of the side of pan.
In a small bowl, whip together yogurt and egg until smooth. Stir in apple and spoon over batter in pan. Mix together the 1/4 cup of sugar and the 1/4 teaspoon of cinnamon; sprinkle over apple mixture.
Bake approximately 45 to 50 minutes or until center is set and crust is deep golden brown. Cool 10 minutes. Remove sides from pan if using springform and serve warm.