Preheat oven to 350 degrees, and fill a muffin pan with cupcake liners.
Add butter to bowl of standing mixer and beat on medium high speed. Slowly pour in granulated sugar and continue to mix until light, fluffy and well combined.
Add in eggs, one at a time.
Turn mixer down to slowest speed. Carefully add in flour, lime zest, baking powder, baking soda and salt then add in Frozen BACARDI ® Mixers Margarita flavor, tequila, lime juice and oil and mix until just combined. Don't overmix!
Using an ice cream scooper, fill each cupcake liner ¾ full and bake for 20-22 minutes or until a toothpick inserted in the center of a cupcake comes out clean.
Place cupcake pan on cooling rack for 10 minutes.
For the buttercream icing:
Add berries to a food processor or heavy duty blender and blend until smooth puree develops. Set aside.
Add butter to bowl of your stand mixer on low speed. Slowly add in confectioner's sugar. Once incorporated, turn mixer up to medium high speed.
Add in vanilla extract and salt.
Lastly, add 2-3 tablespoons of puree to the buttercream and mix until fluffy and smooth.
Pipe buttercream on cooled cupcakes and garnish with sugar crystals if desired.