Stir 2 teaspoons instant espresso into warm water until fully dissolved. Set aside.
In a clean bowl, sift flour, baking powder and cocoa powder. Add in the salt and sugar and ½ teaspoon instant espresso. Whisk gently to combine.
In a different clean bowl, add the egg, oil, vanilla and espresso. Whisk to combine.
Pour the dry ingredients into the wet ingredients. Whisk well to combine. Set aside until ready to use. If you prefer, you can pop this bowl into the fridge while you prepare the orange cake batter.
Orange Cake Batter
Zest two oranges into a small bowl, avoiding the white pith. In a separate small bowl or cup, juice both oranges.
In a clean bowl, combine the flour, baking powder, sugar and salt. Whisk gently to combine.
In a separate clean bowl, add the egg, oil, vanilla, orange juice, orange zest and orange emulsion. Whisk to combine.
Pour the dry ingredients into the wet ingredients and whisk well to combine.
Marbling the Cupcakes
Preheat the oven to 325°F.
Using paper or silicone liners, line one full-size cupcake pan.
Using two small spoons, scoop a bit of orange batter into the bottom of the cupcake tins, then add some espresso, alternating however you'd like. This is the fun part! Get creative and layer however you'd like. Stop filling the cups when it reaches halfway.
TO MAKE CAKE: line a 9" cake pan with parchment and add batter as you would for cupcakes.
Using a toothpick, swirl the batters together in fun and interesting patterns. There's really no wrong way to do this, so have fun with it and experiment freely.
Bake at 325°F for 20-25 minutes or until the tops are firm and a toothpick inserted into the middle of a cupcake comes out clean. (Same baking time for cake)
Prepare the Buttercream
Using a stand or hand mixer, beat the butter until it is soft and fluffy about 5-7 minutes. Using room temperature butter will help speed up this process.
Incorporate powdered sugar ½ cup at a time, waiting until fully combined before adding more.
Once all the powdered sugar is mixed in, add the salt and vanilla extract. At this point, scrape down the sides of the bowl to make sure everything is fully combined.
Pour the whipping cream in a slow, steady stream while beating the buttercream.
If you prefer your buttercream to be plain vanilla flavor, you can skip this step. To get the full orange espresso flavor, add the espresso powder, orange zest and orange emulsions, mixing until fully combined.
If you don't have a piping bag, you can cut one corner off a Ziploc bag and use it to pipe, or simply spread the frosting onto the cupcakes with a butter knife.
Once the cupcakes have cooled fully, frost your cupcakes however you'd like. Incorporate some food dye into the buttercream for an extra burst of color!
Use Betty Crocker cream cheese frosting and add 1 tsp instant espresso (or coffee) and 1 tsp orange zest. Mix to combine and enjoy!