Preheat oven to 375 degrees.
Prepare 2 donut pans with baking spray.
In a medium saucepan, combine 1/4 c. butter, brown sugar, and crushed pineapple. Cook over medium heat until butter is melted.
Divide mixture evenly among 2 donut pans (12 donuts).
In a separate mixing bowl, combine cake flour, sugar, baking powder, cinnamon, and salt.
Add milk, yogurt, egg, melted butter, and vanilla and stir until blended.
Spoon into donut pans, filling 2/3 full.
Bake at 375 degrees for 10-12 minutes or until tops spring back when lightly touched.
Cool 10 minutes in pan; loosen edges and invert onto cooling rack. *Place cooling rack directly on top of donut pan and flip quickly, then gently lift pan to release donuts.