Preheat the oven to 325F. Line a cupcake pan with paper liners.
In a medium bowl, whisk together the flour, baking powder and salt
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar on medium-high speed until light and fluffy, 3-5 minutes.
Blend in the eggs one at a time, mixing well after each addition and scraping down the sides of the bowl as needed. Beat in the lime zest, lime juice and vanilla.
With the mixer on low speed, mix in the dry ingredients in three additions alternating with the buttermilk, beginning and ending with the dry ingredients. Beat each addition just until incorporated.
Divide the batter between the prepared cupcake liners, filling each about ¾ full. Bake 20-24 minutes, or until a toothpick inserted in the center comes out clean. Let cool in the pan 5-10 minutes, then transfer to a wire rack to cool completely
Meanwhile make the filling:
In a small saucepan, combine the strawberries, lime zest/juice, sugar and cornstarch. Cook over medium-high heat, stirring constantly until mixture becomes thick and jam-like, and the strawberries start to soften.
At this point- either use an immersion blender directly in the pot, or transfer mixture to a blender or food processor to puree.
Return mixture to the pot and cook for 5-10 minutes on medium heat, stirring frequently until reduced and thick. Stir in all but a splash of the ¼ cup of tequila. Let cool completely.
Filling the cupcakes:
Using a small paring knife, cut a cone out of the top of each cupcake. Remove the cut-out cake and spoon a tablespoon of strawberry filling into each cupcake. (Make sure to reserve at least 2 tablespoons for the frosting!) Replace the top part of the cone, cutting the tip to leave room for the filling.
For the Frosting:
In a large mixing bowl, cream the butter on high until fluffy. Add the powdered sugar one cup at a time. Cream in the strawberry filling and the remaining splash of tequila. Mix until the frosting is thick and creamy, adding a splash of milk or lime juice if needed. If the frosting seems to curdle, add a little more powdered sugar until smooth.
Spread or pipe on cupcakes. Use a spoon to sprinkle some coarse sugar around the edge of the cupcake and top with a strawberry slice and lime wedge.