Step 1

Preheat oven to 350°. Butter and flour bottom and sides of a glass 13x9" baking dish.

Step 2

Whisk 1½ cups flour, baking powder, and cinnamon in a large bowl. Using an electric mixer, beat egg whites in another large bowl until stiff peaks form, 7–8 minutes. Gradually beat in sugar. Add egg yolks one at a time, beating to blend between additions. Beat in 2 tsp. vanilla. Add flour mixture in 3 additions, alternating with whole milk in 2 additions, beginning and ending with flour mixture. Pour batter into pan; smooth top.

Step 3

Bake cake for 25 minutes. Reduce heat to 325°; continue baking until cake is golden brown and middle springs back when pressed, 20–25 minutes more. Let cake cool in pan for 15 minutes. Invert cake onto a wire rack set inside a rimmed baking sheet.

Step 4

Whisk ½ tsp. vanilla, evaporated milk, and remaining ingredients in a medium bowl. Poke holes all over top of cake with a skewer. Slowly drizzle half of the evaporated milk mixture over cake, letting liquid soak in before adding more. Let cake sit for 10 minutes.

Step 5

Invert a platter on top of cake. Lift rack and gently invert cake onto platter. Drizzle remaining sauce over. Spoon any liquid collected on sheet over cake.