Preheat oven to 375*.
Lightly grease a 9" springform pan; line bottom with parchment or waxed paper.
In a bowl, combine the rhubarb, apples, raspberries, blueberries and 2 tbls of the sugar. Mix well; set aside.
In another bowl, combine the flour, 1/2 cup of the remaining sugar,baking powder, baking soda, salt and nutmeg. Add the butter or vegetable shortening and cut it in till fine crumbs form. Stir in lemon rind.
Make a well in the center.
In another bowl, combine the eggs with yogurt and mix to combine. Pour the egg mixture into well and stir just until dry ingredients are moistened.
Spoon half of the batter into a prepared pan. Arrange the fruit mixture over the top, leaving 1" border uncovered.
Spoon remaining batter evenly over the top and spread to cover the fruit.
Brush the top with melted butter; sprinkle with the remaining sugar. Bake on baking sheet in the center of the oven for about 1 hour or until golden brown.
Let cool in pan on rac for 10 minutes. Remove sides of pan and cool completely.Serves 8.