Pineapple Upside-Down Cakes

Prepare pineapple layer:

-Preheat oven to 350 F

-Melt butter in saucepan over low heat, add brown sugar and cook, whisking, until mixture is smooth and combined well, about 1 minute

-Divide mixture among muffin cups (about 1 1/2 tbsp per cup, then put 1 pineapple slice in each cup

Make cake batter:

-Sift together flour, baking powder, and salt in bowl. Wisk milk and vanilla in a small bowl.

-Beat butter with sugar in large bowl at medium speed until pale and fluffy, about 5 minutes. Add yolks 1 at a time, beating well after each addition. Reduve speed to low and add flour mixture and milk mixture alternately in batches, b eginning and ending with flour mixture and mixing until just combined.

Bake cakes: Divide batter evenly among cups and bake in middle of oven until puffed and pale golden, about 25-30 minutes. Cool cakes on rack 15 min. Loosen sides of cakes with a parine knife and invert onto rack to cool ro warm or room temp.