Make the Cupcakes:
Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners.
In a large bowl, whisk together the flour, baking powder, salt, and ground cardamom. Set aside.
In the bowl of a stand mixer, cream together the butter and sugar until light and fluffy, about 3 minutes.
Add the eggs one at a time, beating well after each addition.
In a small bowl, mix the milk and vanilla extract. With the mixer on low, alternate adding the flour mixture and the milk mixture to the batter, beginning and ending with the flour mixture. Mix until just combined.
Stir in the pureed strawberries until fully incorporated.
Divide the batter evenly among the cupcake liners, filling each about ¾ full.
Bake for 20-25 minutes, or until the tops spring back when touched and a toothpick inserted into the center comes out clean.
Let the cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
Make the Swiss Meringue Buttercream:
In a heatproof bowl, whisk together the egg whites and sugar. Set the bowl over a pot of simmering water, ensuring the bottom of the bowl does not touch the water. Whisk constantly until the sugar dissolves and the mixture reaches 160°F (71°C).
Remove the bowl from the heat and transfer to a stand mixer. Whisk on medium-high speed for 5 minutes, or until stiff peaks form.
Reduce the speed to medium and gradually add the butter, one piece at a time, until fully incorporated. Add the chopped basil and continue whisking until stiff peaks reform.
Switch to the paddle attachment and, on low speed, slowly add the pureed strawberries. Mix until fully combined. Whisk on medium speed if the buttercream needs to firm up.
Assemble the Cupcakes:
Once the cupcakes have cooled completely, frost them with the strawberry basil buttercream. For an elegant touch, garnish with any leftover strawberry puree and edible rose petals.