Preheat the oven to 350°F. Grease a 9 x 13-inch baking dish with nonstick baking spray and set it aside.
Prepare the wet ingredients. In the bowl of an electric mixer, combine the butter and sugar. Mix on medium until it is light and fluffy, 3-5 minutes. With the mixer on medium-low, add the eggs, one at a time, allowing each to incorporate, followed by the vanilla extract.
16 tbsp (2 sticks) unsalted butter, 1 ½ cups granulated sugar, 3 large eggs, 2 tsp vanilla extract
Add the dry ingredients. Add the flour, baking powder, and salt. Turn the mixer on medium-low and slowly add the buttermilk until everything is just incorporated. Do not overmix; a few dry streaks are okay. Remove the bowl from the mixer and fold the batter a few times with a spatula. Pour into the prepared baking dish.
Bake the cake. Bake in the preheated 350°F oven until a skewer inserted in the middle comes out clean, 35-45 minutes. Remove from the oven and cool for 20 minutes. Once the cake is slightly cooled, use a large skewer to poke holes all over the cake. Insert the skewer all the way to the bottom of the pan.
While the cake is baking, prepare the gelatin according to the package instructions. Set aside to cool to room temperature, 20-30 minutes. Then, slowly and evenly pour the prepared gelatin over the cake with the poked holes. Refrigerate until fully chilled, 2-3 hours.
1 3-oz pkg strawberry gelatin
Once the cake is chilled, prepare the topping. In a large bowl, whip the heavy cream, powdered sugar, Greek yogurt, and vanilla extract until it reaches stiff peaks. Spread the whipped cream over the cake. Refrigerate for at least 1 hour or overnight. Before serving, top with sliced strawberries.
Serving: Chill for at least 1 hour after frosting for the best texture. Slice into 15 or more pieces, as this cake is sweet!Storage: Keep leftovers in an airtight container in the fridge for 5–7 days. Great for making ahead!