Preheat oven to 350 F 

Combine lemon juice and coconut milk - set aside for 10 minutes while you put together batter. This is your vegan "buttermilk."

Using a stand mixer with the whisk attachment, mix softened butter and oil together for 3 minutes or until well combined and homogenous. 

Add granulated sugar slowly, allowing it to incorporate, then mix for another 3 minutes. 

Tablespoon by tablespoon, add aquafaba/seltzer water mix, then vanilla extract. Beat for another 3 minutes. 

In a separate bowl, sift dry ingredients. 

In 4 batches, alternate adding the "buttermilk" (coconut milk and lemon) with dry ingredients, starting with buttermilk, and ending with dry ingredients. 

If desired, stir in sprinkles. BEWARE the colors might bleed a bit. 

Line your muffin pan with cupcake liners, and scoop batter into the liners. My scoop is ~¼ cup, maybe a little more. 

Bake at 350 F for 20-30 minutes, testing with a toothpick or knife (when it comes out clean, your cupcakes are probably ready). 

Cool in pan for 5-10 minutes, then on a cooling rack for at least 2 hours before frosting. 

For the frosting: 

Add softened butter, powdered sugar and vanilla extract to a stand mixer bowl with whisk attachment. Start on low, and build up speed as powdered sugar mixes in. 

Transfer into a piping bag if desired, or ice using a knife or offset spatula. If icing is too thin, put in the freezer for 5-10 minutes. 

Store frosted cupcakes in the refrigerator, and enjoy!