Preheat the oven to 350°F. Using 1 tbsp of butter, grease a 10-inch cast iron skillet.
In a medium bowl, toss together the strawberries, sugar, and lemon zest. Set it aside.
In a large bowl, stir together the flour, sugar, baking powder, and salt.
Create a well in the center of the dry ingredients and add the buttermilk, egg, and vanilla extract. Fold together until you have a sticky biscuit dough.
Add the dough to the greased skillet and spread it out evenly.
Bake for 25-30 minutes, or until the top is golden brown.
Let the cake rest for 10 minutes, then serve with strawberry sauce and optional toppings of vanilla ice cream or whipped cream.