Dirty Horchata Tres Leches Cake

1. Preheat oven to 350 degrees F. Butter an 8x8 inch square baking pan. 2. In a large bowl, whisk together the egg yolks, melted butter, milk, and vanilla. Whisk in the flour, 1/4 cup sugar, the baking powder, 1/4 teaspoon cinnamon, and the salt. The batter will be very thick. 3. In a separate bowl, using an electric mixer, whip the egg whites on medium speed until frothy, about 2 minutes. Add 2 tablespoons of sugar, a little at a time, and continue beating until the whites are glossy and stiff peaks form, another 3 to 5 minutes. Fold about 1/4 of the whipped egg whites into the yolk mixture to loosen it. Gently fold in the remaining egg whites. 4. Transfer the batter to the prepared pan, spreading it in an even layer. Bake 15-18 minutes, until the center is no longer jiggly. Remove from the oven and let sit 10 minutes. Let cool 15 or so minutes. 5. Meanwhile, make the glaze. In a medium bowl, whisk together the rice milk, coconut milk, sweetened condensed milk, 1/2 teaspoon cinnamon, and rum (if using). 6. Use a fork to poke holes all over the top of the warm cake. Pour the milk mixture evenly over the cake. Cover and chill cake for at least 4 hours or overnight (or up to 3 days).7. No more than 4 hours before serving, whip the cream and powdered sugar together using an electric mixer on medium-high speed until soft peaks form, 2 to 3 minutes. Divide the whipped cream in half. Stir the instant coffee and Kahlúa into half of the whipped cream. Dollop both the plain cream and coffee cream over the cake and gently spread, swirling the two together. Sprinkle with more cinnamon. Serve and enjoy!