Ruby's Strawberry Jell-O® Flan Cake

Preheat oven to 350 degrees F (175 degrees C). Spray a fluted cake pan (such as Bundt®) with cooking spray.

Beat cake mix, 1 cup water, vegetable oil, and 3 eggs together in a bowl with an electric mixer on low speed for 30 seconds. Increase speed to medium and beat until batter is smooth, about 2 minutes.

Beat condensed milk, evaporated milk, 4 eggs, and vanilla extract together in another bowl until flan mixture is smooth, about 3 minutes. Pour into prepared cake pan. Pour 3/4 of the strawberry cake batter on top of the flan mixture. Set cake pan in a roasting pan. Pour water into the roasting pan to read halfway up the sides of the cake pan.

Bake in the preheated oven until a knife inserted into the center of the cake comes out clean, 45 to 55 minutes. Cool to room temperature, about 30 minutes. Refrigerate until chilled, at least 6 hours.

Place a plate on top of the cake pan and invert to loosen cake. Flip cake pan and plate back to return cake to the pan.

Combine boiling water and gelatin in a bowl; stir until gelatin is dissolved. Pour 1 cup cold water into gelatin mixture. Let cool until gelatin mixture is warm to the touch. Pour gelatin mixture into the cake pan along the sides so that the gelatin runs under the cake and cake begins to float. Refrigerate until set; at least 5 hours.

Remove cake from refrigerator and place pan in hot water to loosen from the sides of the cake pan. Invert onto a serving plate.