Preheat oven to 325°F. Lightly grease a 9x5-inch loaf pan, then line the bottom and sides with parchment paper, leaving an overhang on the long sides to easily lift the loaf out after baking.
In a large bowl, whisk together sour cream, oil, and melted butter until smooth.
½ cup sour cream or full-fat Greek yogurt, ½ cup neutral oil, 2 Tbsps unsalted butter
In a separate bowl, combine sugar and lemon zest. Press together with the back of a spoon to release the oils, then stir into the wet mixture.
1 cup granulated sugar, 4 Tbsps finely grated lemon zest
Whisk in eggs, lemon juice, and lemon extract (if using).
2 large eggs, 3 Tbsps lemon juice, ½ tsp lemon extract
In another bowl, whisk flour, baking powder, baking soda, and salt. Fold into the batter until just combined.
1 ½ cups all-purpose flour, 1 tsp baking powder, 1 tsp kosher salt, ¼ tsp baking soda
Pour into prepared pan and smooth the top.
Bake for 45–50 minutes, or until the center feels set and a toothpick inserted in the center comes out clean. Do not open the oven before 40 minutes.
Let cool 5 minutes, then poke holes all over the loaf.