Step 2: Beat flour, sugar, shortening, baking powder, salt, milk, and egg on low speed for 1 minute, scraping bowl. Beat on high speed an additional 3 minutes, again scraping bowl down. Pour batter over pineapple. Step 3: Bake 25 to 30 minutes or until toothpick inserted in each cake comes out clean. Immediately place sheet pan over muffin pan; invert. Leave muffin pan over sheet pan so brown sugar mixture can drizzle over cake. Serve while warm with tres leches ice cream.