Preheat the oven to 350F (180C) degrees. Line a 9 x 5 inch (23 x 13 cm) or an 8 1/2 x 4 1/2 inch (21.6 x 11.4) loaf pan with parchment paper, or line the bottom and grease any exposed sides.
In a medium bowl whisk together the melted butter, oil, sugar, eggs, vanilla extract, lemon extract, lemon zest, lemon juice and sour cream. Whisk together until you no longer see pieces of egg or lumps of sour cream.
In a large bowl whisk together the flour, baking powder and salt. Make a well shape in the bowl.
Pour the wet ingredients into the well created in the dry ingredients. Then mix together with a rubber spatula or wooden spoon. Do a few whisks with a wire hand whisk to remove any large lumps. When finished, you should no longer see streaks of flour.
Pour the batter into the prepared loaf pan and smooth the top.
Bake in the middle of the preheated oven for about 50-60 minutes if using an 8 1/2 x 4 1/2 inch pan or about 45-55 minutes if using a 9 x 5 inch pan. Check the loaf around 40 minutes, if the top is already golden, tent a piece of aluminum foil overtop. When the loaf is done baking an inserted toothpick should come out clean or with a few moist crumbs but no batter. If you are unsure, bake for a few extra minutes.
Remove from the oven and cool the loaf in the pan for at least 30 minutes, then carefully remove from the pan and continue cooling on a wire rack.