Combine 2 cups flour, 1/2 cup sugar, baking powder, and salt in a large bowl; make a well in center of mixture.
Stir together yogurt and next 3 ingredients; add to dry ingredients, stirring just until moistened.
Toss together 2 tablespoons flour and raspberries; fold into batter. Spoon into lightly greased muffin pans, filling two-thirds full.
Combine remaining 2 tablespoons flour and 3 tablespoons sugar; cut butter into mixture with a pastry blender or fork until crumbly. Spoon evenly over batter in muffin pans.
Bake at 375° for 20 to 25 minutes or until golden. Remove muffins from pans immediately, and cool on wire racks.
*Blueberries may be substituted for raspberries.