In a large mixing bowl, combine gluten-free flour blend, salt, and ground cardamom. Rub in cold, diced unsalted butter until the mixture resembles coarse breadcrumbs. Stir in the sugar and lime zest. Add the egg and lime juice, mixing until a slightly tacky dough forms. Wrap in plastic wrap and chill for at least 30 minutes to firm up.

Preheat your oven to 200°C (400°F). Roll out the chilled pastry to fit a pie tin, gently pressing it into the edges. Chill for 10 minutes before covering with parchment paper and filling with pie weights. Blind bake for 10 minutes, then remove weights and bake for an additional 7-10 minutes until golden and dry. Allow to cool completely.

In a medium saucepan, combine sliced strawberries, rhubarb, and lime juice. Simmer over medium heat for about 5-7 minutes until softened. Strain to obtain a puree, return it to the saucepan, mix sugar and cornstarch with a splash of water, add to puree, heating gently while stirring until thickened.

Remove saucepan from heat, stir in butter and egg yolks until fully combined. Pour the filling into cooled pie crust, smoothing the top with a spatula. Refrigerate for at least 30 minutes to set.

In a clean, dry bowl, whisk egg whites until soft peaks form. Gradually add sugar while whisking until stiff, glossy peaks form, about 5-7 minutes.

Spread or pipe meringue over the hot fruit filling, sealing the edges to prevent shrinking. Preheat oven to 180°C (350°F) and bake for about 20 minutes, or until meringue is golden brown.