First, make your guava pudding. In a small saucepan, combine the guava puree and heavy cream and simmer over medium-low heat for a few minutes. Separately, in a medium bowl, combine the sugar, corn starch, eggs, and salt and whisk to combine. Once the guava is hot, scoop 1/4 cup of the hot mixture and whisk it quickly into the bowl with the egg mixture (to temper the eggs). Then, stirring constantly, slowly add the egg mixture into the simmering guava pot and continue to stir until thicker and bubbling (about 3-4 minutes). Once it's thicker, remove the pot from the heat and add the butter and vanilla and continue to stir until silky and smooth. Pour into a container and refrigerate for about 2 hours or until set and completely cool (this can be made ahead and kept in the fridge for up to a week).
Then, make your cupcakes. Preheat the oven to 350° F and line two 12-cupcake pans with paper cupcake cups. In a medium bowl, whisk together all of the dry cupcake ingredients (flour, almond flour/meal, baking soda, baking powder, salt), then set aside. Then, in a large bowl, whisk together the wet ingredients (eggs, oil, sour cream, guava puree, sugar, vanilla) until combined. Pour the whisked dry ingredients into the wet ingredients and stir together until smooth. Add a small amount of pink food coloring if you want and stir to combine. Spoon a tablespoon of the cupcake batter into each of the cupcake cups and save the remaining batter.
Then, make your cheesecake swirl. In a medium bowl, using an electric mixer, beat the cream cheese and sugar until smooth, then add the egg, vanilla, and sour cream and beat until creamy - 1-2 minutes. Spoon a heaping teaspoon of the cheesecake mixture on top of the batter in the cupcake cups, then spoon in the remaining batter to cover the cheesecake. You can swirl the cheesecake filling a bit if you want with the batter. Bake cupcakes for 25-28 minutes or until a skewer inserted into the center of a cupcake comes out clean. Let cool completely before frosting.
While the cupcakes are cooling, make the buttercream. In a large bowl, using an electric mixer, beat your room temperature butter, shortening, and cream cheese for 4-5 minutes until creamy and lighter. Add 2 cups of the sifted powdered sugar and beat until smooth. Add the vanilla and the cooled guava pudding and continue to beat until creamy. Continue adding more of the powdered sugar until combined, then add pink food coloring (optional) and beat to combine. Scoop buttercream into a pastry bag and pipe onto cooled cupcakes, then serve!