Preheat the oven to 350 degrees F. Line a 9 x 13" baking pan with parchment paper or use a bit of oil spread over the surface.
If you have a food processor, use it to combine 2 cups of flour, 1/2 cup of sugar, butter, and a pinch of salt. Pulse until the dough comes together in large crumbs. If you don't have a processor, just mix by hand. Press the dough evenly into the bottom of the lined or greased baking pan. Bake until just lightly golden, about 20 minutes.
Combine the filling ingredients, eggs, the rest of the sugar, lemon juice, a cup of flour, and 1/4 tsp salt in a food processor (or by hand) and pulse until evenly blended and smooth.
Pour the filling on top of the shortbread crust and bake about 35 minutes or until the filling is set and the top is beginning to brown. Let cool to room temperature, and then transfer to the refrigerator. Chill for at least an hour before cutting.
Cut the lemon bars as desired. Combine the blueberries, powdered sugar, ½ tablespoon of the lemon zest, and the basil in a food processor and process until smooth.
Transfer the lemon bars to a wire rack and top with the glaze, allowing the excess to drip onto foil or paper below the rack. Sprinkle with the remaining lemon zest and top with blueberries. Let the glaze set and then serve.