Preheat the oven to 375 degrees Fahrenheit. Line a muffin pan with cupcake liners and set aside.
In a medium-sized bowl, stir together the flour, baking powder, salt, and baking soda.
In a separate large bowl, whisk together the melted butter, vegetable oil, and granulated sugar. Whisk in the eggs. Add the sour cream, buttermilk, lemon juice, and lemon zest, and whisk until combined.
Add the dry ingredients to the wet batter and stir together until just combined.
Divide the batter evenly between the liners, about 3 tablespoons of batter each. Bake for 5 minutes in the preheated oven, then lower the temperature to 350 degrees Fahrenheit and bake an additional 10-12 minutes until a toothpick inserted into the center comes out clean.
Let the cupcakes cool slightly in the muffin pan before placing on a wire rack to cool completely.
To make the strawberry buttercream, beat the softened butter over medium speed with an electric mixer until creamy. Continue to beat over medium speed as you gradually add the powdered sugar and salt. Stop the mixer and scrape down the sides of the bowl with a spatula as needed to fully incorporate all of the sugar. Add the strawberry puree, vanilla extract, and strawberry extract if using. Beat over medium speed until frosting is light and fluffy. Frost the cupcakes and add any desired toppings such as sliced strawberries, lemon wedges, or sprinkles.