Heat oven to 350°F (175°C). Line a 9×13-inch light-colored metal pan with parchment with overhang on two sides. Lightly grease parchment and sides.
Cream butter with granulated and powdered sugars and salt until smooth. Mix in flour just until a crumbly dough forms. Press firmly into an even layer in the pan and dock lightly with a fork.
Bake crust 18–20 minutes until edges are lightly golden and surface looks dry. Reduce oven to 325°F (163°C).
Whisk eggs with granulated and powdered sugar and salt until combined with minimal foam. Whisk in flour until smooth, then whisk in Meyer lemon juice, zest, and melted butter until glossy and lump-free.
Pour lemon mixture over the hot crust. Bake at 325°F for 18–22 minutes until the center barely jiggles like set gelatin and an instant-read thermometer in the center reads about 170°F.
Cool on a rack to room temperature, then chill at least 2 hours. Lift out by parchment, dust with powdered sugar, and slice with a hot, damp knife, wiping between cuts.