Preheat oven to 350 degrees F. Spray cups of 12 cup standard sized cupcake pan with nonstick cooking spray.
To make batter:
Using a mixer, combine butter, sugar and lemon zest. Beat at medium speed for 5 minutes or until mixture is very light, pale and fluffy, stopping 2 or 3 times to scrape bowl. Into another bowl, sift together flour, baking soda and salt. Set aside. One at a time, beat eggs into butter mixture until fully incorporated, stopping after each addition to scrape bowl. Beating continuously, add 2 tablespoons lemon juice. Beat until fully incorporated. On low speed, alternately beat in buttermilk and sifted flour mixture in 3 batches until fully incorporated.
To bake cupcakes:
Spoon batter into muffin cups. Bake for 10-15 minutes or until deep golden brown and slightly firm to light touch. Insert toothpick into center of cupcake and comes out clean. Note: rotate pan 180 degress halfway through cooking.
To make lemon syrup:
Put sugar and lemon juice in nonreactive saucepan. Stirring frequently, cook over med-high heat until sugar dissloves completely and mixture comes to a boil. Immediately reduce heat. Simmer briskly, stirring occasionally, until mixture has thickened to syrupy but still pourable consistency.
To brush on lemon syrup:
Remove cupcakes from oven. Place on wire rack. Using thin skewer, poke holes all over hot cupcakes. Generously and repeatedly brush lemon syrup over cupcakes until they have soaked up as much syrup as possible. (Note: Any leftover syrup can be refrigerated and used to sweeten other desserts or iced tea.).