Preheat the oven to 350 degrees Fahrenheit.
Wash and cut the tops off the strawberries. Set aside the 4 largest strawberries and dice them, then cut the remaining strawberries in half and puree them in a blender. Set aside 1/2 cup of the strawberry puree for the cupcake batter, then save the remaining puree for the frosting.
In a large microwave-safe bowl, melt the butter. Add the granular Swerve and beat with a hand mixer. Add the eggs, sour cream, 1/2 cup of strawberry puree, and vanilla, and beat until well mixed.
In a medium bowl, toss together the almond and coconut flour with the baking powder and salt. Add 1/3 of the mixture to the wet ingredients and beat with a hand mixer until just incorporated. Repeat with the remaining 2/3 of the dry ingredient mixture, making sure not to overbeat. Fold in the diced strawberries.
Line 12 cupcake tins with cupcake liners. Pour the batter evenly into the cupcake liners, filling about 3/4 full. Bake for 27-30 minutes, testing the centers with a toothpick to make sure they're cooked through. When finished, remove from the oven and let cool completely before handling or frosting.