Prep the pan and oven. Heat your oven to 350°F (175°C). Line a 9x9-inch baking pan with parchment, leaving overhang for easy lifting.
Lightly grease the sides.
Make the crust. In a bowl, whisk the gluten free flour, powdered sugar, and salt. Stir in the melted butter, vanilla, and lemon zest until a soft dough forms.
Press and pre-bake. Press the dough evenly into the lined pan. Use the bottom of a measuring cup to flatten.
Bake for 15–18 minutes, until set and lightly golden at the edges.
Beat the cream cheese. In a mixing bowl, beat the softened cream cheese until smooth and lump-free, about 1–2 minutes. Scrape the bowl.
Mix the filling. Add sugar and beat until creamy. Add the eggs one at a time, mixing just to combine.
Beat in lemon juice, lemon zest, flour or cornstarch, salt, and vanilla until smooth. Do not overmix.
Pour and bake. Pour the filling over the hot crust. Gently tap the pan once to release bubbles.
Bake 20–24 minutes until the center is set and only slightly jiggles.
Cool and chill. Cool the pan on a rack for 30–45 minutes. Then chill at least 2 hours, or until fully set. Lift out using parchment and slice into bars.
Finish and serve. Dust with powdered sugar and garnish with lemon zest right before serving.