Place an oven rack in the center of the oven; preheat to 350°F. Line an 8-inch square baking dish with parchment paper (extending it over the sides so the bars are easier to transfer). Wash and dry the fresh produce. Using a zester or the small side of a box grater, finely grate the lemon to get 2 teaspoons of zest (reserve the lemon for future use if desired). Melt the butter in a large bowl in the microwave (or melt in a small pot on the stove, then transfer to a large bowl). Add the sugar, lemon zest, and a pinch of salt; whisk to combine. Add the all-purpose flour, almond flour, vanilla powder, and rice flour; stir to thoroughly combine. Transfer to the baking dish. Using the bottom of a glass or measuring cup, press into an even layer. Bake 17 to 19 minutes, or until lightly browned around the edges. Leaving the oven on, remove from the oven. Let stand 5 minutes.

Transfer the par-baked shortbread (in the parchment) to a cutting board and cut into 12 equal-sized pieces. Line a sheet pan with parchment paper. Carefully transfer the bars to the sheet pan. Bake 10 to 12 minutes, or until lightly browned and cooked through. Remove from the oven and let cool completely (for quicker cooling, place in the refrigerator).

Once the bars have cooled, in a microwave-safe bowl, combine the chocolate chips, 2 teaspoons of oil, and a pinch of salt. Working in 30 second increments, microwave on high, stirring in between, until melted and smooth. Drizzle the cooled shortbread with the melted chocolate. Transfer to the refrigerator and let set about 20 minutes before serving. Enjoy!