In a bowl, sift together the flour, baking powder, and salt
In an electric mixer bowl, whisk 1 cup of sugar, the eggs, lemon zest, and vanilla
Slowly add in the dry ingredients
Fold in the vegetable oil with a spatula, making sure it is fully mixed-in
Pour into loaf pan and bake 50 minutes. until a toothpick comes out clean.
Remove from oven and let cool 10 minutes.
Syrup
While the cake is cooling, make the lemon syrup, Add the ⅓ cup of sugar, lemon juice, and 2 tbsp Limoncello to a heavy bottom sauce pan on medium heat.
Stir and cook until sugar dissolves.
When the cake has cooled 10 minutes, spoon the lemon syrup over the cake.
Let the cake continue to cool in the loaf pan about an hour
Frosting
To make the frosting, place the the powdered sugar, room temp butter, 2 tbsp Limoncello, milk, vanilla, and salt in the bowl of an electric mixer with the paddle attachment and mix until smooth and creamy.
Remove the cake from the loaf pan and frost.
Notes
Limoncello is a Sicilian Liqueur. I buy mine at Trader Joe's. You can replace the Limoncello with lemon juice if you don't want to use a liqueur.
My favorite frosting
This is my go-to easy frosting. You can make it as thick or thin as you like, and any flavor you like. It also works well with food coloring.