Step 1: Preheat oven to 350°F (175°C). Grease and flour three 8-inch round cake pans. Line the bottoms with parchment paper.
Step 2: In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
Step 3: In a large bowl, cream together the softened butter and 2 cups granulated sugar with an electric mixer until light and fluffy, about 3-5 minutes.
Step 4: Beat in the eggs one at a time, mixing well after each addition. Stir in 1 tbsp vanilla extract.
Step 5: Gradually add the dry ingredients to the wet ingredients in three additions, alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined.
Step 6: Divide the batter evenly among the prepared cake pans. Bake for 25-30 minutes, or until a wooden skewer inserted into the center comes out clean. Let cool in pans for 10 minutes, then invert onto a wire rack to cool completely.
Step 7: For the cherry filling, combine cherries, 1/2 cup granulated sugar, lemon juice, and cornstarch in a medium saucepan. Cook over medium heat, stirring, until thickened and gently boiling. Remove from heat and cool completely.
Step 8: For the salted caramel sauce, combine 1 1/2 cups granulated sugar and water in a heavy-bottomed saucepan. Cook over medium heat without stirring until the sugar dissolves and turns a rich amber color (8-10 minutes).
Step 9: Remove from heat. Slowly and carefully pour in the warm heavy cream, whisking constantly until smooth. Stir in 1/4 cup softened butter and sea salt until fully incorporated. Let cool completely until thickened.
Step 10: For the cream cheese frosting, beat softened cream cheese and 1 cup softened butter in a large bowl until smooth and creamy.
Step 11: Gradually add the sifted powdered sugar, 1 cup at a time, beating until smooth. Add 2 tsp vanilla extract. If needed, add 2-4 tbsp heavy cream for desired consistency.
Step 12: To assemble, place one cooled cake layer on a serving plate. Spread with 1/3 of the cream cheese frosting. Drizzle with 1/4 cup of cooled caramel sauce. Spoon half of the cherry filling over the caramel.
Step 13: Repeat with the second cake layer, frosting, caramel, and remaining cherry filling.
Step 14: Top with the third cake layer. Frost the top and sides of the entire cake with the remaining cream cheese frosting.
Step 15: Chill the cake for at least 30 minutes to set the frosting.
Step 16: Drizzle the remaining salted caramel sauce generously over the top of the cake, allowing it to drip down the sides. Garnish with fresh cherries if desired. Slice and serve.