For donuts: Preheat oven to 325°F. Spray donut pan with non-stick spray. Set aside. In a large bowl, mix together flour, sugar, and baking powder. Set aside. In a small bowl, whisk together yogurt, milk, egg, vanilla and melted butter. Slowly mix wet ingredients into dry – just until fully combined (do not overmix).
Use a pastry bag fitted with a large round tip (or Ziploc bag with corner cut off) to pipe the batter into a 6-donut pan. Fill the cavities about 2/3 full. Bake 10-12 minutes, or until donuts are set and golden brown.
Allow to cool slightly before removing from pan, about 5 minutes. Dip donuts into strawberry frosting 1-3 times, depending on desired thickness.
For frosting: Slice strawberries and puree with 1 tablespoon strawberry jam. Slowly stir in 1 cup sifted confectioners’ sugar, adding more until you reach desired thickness and consistency. Donuts are best served immediately. Store leftovers in airtight containers for up to 2 days.