Position a rack in the center of the oven. Preheat the oven to 350°F (180oC). Grease with nonstick cooking spray or line with parchment paper.
In a large bowl, with an electric mixer cream the butter and sugar together on medium speed, until light and fluffy, about 2 minutes.
Beat in the eggs one at a time. Add the milk and mix until homogeneous. Scrape down the bowl as needed.
On low speed, beat in the baking powder, baking soda, and flour until the last of the flour has been incorporated. Do not overmix.
Pour the cake batter into a 9x13 inch baking dish and bake for 30 minutes, or until a toothpick or skewer inserted comes out clean. Remove from the oven and cool on a wire rack.
Use the handle of a wooden spoon or a large skewer to poke holes scattered throughout the top of the cake.
In a small bowl, whisk together the Jell-O powder and water. Pour the Jell-O mixture over the top of the cake.
Make the frosting. Combine the butter and confectioners sugar in the bowl of your stand mixer. Mix on low speed at first, then increase to medium until combined and smooth. About 2-3 minutes. Add in your heavy cream, salt, and vanilla extract, and mix on medium to high speed for 8 minutes until light and creamy.
Once the cake has cooled, use a spatula to spread the frosting evenly over the top.
Decorate the top of the cake with the sliced strawberries. Slice, serve, and enjoy!