1. Preheat oven to 350°F (175°C). Grease a 9×13-inch pan with butter and dust with flour, or line with parchment paper.

2. Whisk together flour, baking powder, baking soda, and salt in a medium bowl. Set aside.

3. Combine buttermilk, ⅓ cup lemon juice, and vanilla extract in a small bowl. Set aside.

4. Beat butter with electric mixer on medium speed for 1 minute until creamy.

5. Add sugar and 3 tablespoons lemon zest. Beat on medium-high for 4-5 minutes until light and fluffy, scraping bowl frequently.

6. Add eggs one at a time, beating 30 seconds after each addition.

7. On low speed, add flour mixture in three additions alternating with buttermilk mixture in two additions, beginning and ending with flour. Mix each addition just until incorporated.

8. Scrape bowl and give 3-4 gentle stir-throughs with spatula.

9. Pour batter into prepared pan and spread evenly. Tap pan on counter 3-4 times.

10. Bake 35-40 minutes until toothpick inserted in center comes out clean and cake springs back when pressed.

11. Cool in pan on wire rack for 15 minutes.

12. For glaze: Whisk together powdered sugar, ¼ cup lemon juice, melted butter, and 1 teaspoon zest until smooth.

13. Poke holes in warm cake with skewer, pour half the glaze over top. Wait 10 minutes, pour remaining glaze. Or cool completely and pour all glaze at once for glossy finish.