Preheat oven to 350 degrees F. Grease an 8x8 baking dish and line with parchment paper, leaving an overhang on 2 sides to easily lift the bars out of the pan before cutting.
Combine the gingersnap cookie crumbs with melted butter and brown sugar. Press the crumbs into the prepared baking dish into one even layer to form the crust. Bake for 8-10 minutes or until lightly browned. Let cool completely.
Make the filling. Blend the strawberries until smooth to make the strawberry puree and combine with the lime juice.
Beat together the egg yolks with lime zest until frothy, about 5 minutes. Slowly add the condensed milk, beating constantly. Add the lime juice and strawberry puree, mixing until well combined. Pour the filling into the pan with the crust and bake for 10 minutes or until the edges have set. The center will be a little jiggly but it should not be runny. Remove from the oven and let cool completely on a wire rack. Continue to cool in the fridge for at least 4 hours or overnight.
Meanwhile, make the meringue. Whip together the egg whites with cream of tartar until foamy. Gradually add the sugar, whipping until stiff peaks form. Top the strawberry key lime bars with the meringue. Use a blow torch to torch the top of the meringue. Cut into 9 bars and serve.
Notes
This dessert yields a generous amount of meringue. You can choose to make half the amount for a more tart pie bar.