Preheat the oven to 350 and grease and flour a 9x5 plan or line with parchment and grease that. Whisk together the flour, baking powder, salt, lemon zest and true lemon in a bowl.
In a stand mixer, beat the butter until light and fluffy with a paddle attachment. Add the vanilla and lemon juice and sugar and whip until smooth, scraping down the sides. Add the eggs on at a time on medium speed and beat until well mixed, scraping the bowl again.
Add in 1/2 of the flour, along with the buttermilk and sour cream and mix on low until fully combined, scraping down the bowl as needed.
Add the other 1/2 flour mixture and mix on low until just combined. Give a mix by hand to make sure it is all well mixed.
Place in the oven and bake for 20 minutes, then rotate the pan 180 and bake another 20 minutes. Start checking for doneness by making sure the center is fully set and a toothpick comes out clean. If the center is still raw, continue baking another 5-10 minutes. The cake should be golden brown and fully set.
Cool in the pan for 30 minutes, then remove from the pan and cool fully. Mix the glaze to a thick consistency and spread over the cake. Allow to dry, then slice. Store in an airtight container at room temp. It won't last long once you taste it.