Preheat the oven to 350 degrees F.

Butter a 6-cup loaf pan and line it with parchment or waxed paper. 

In a medium bowl, combine the flour, baking powder, and salt.

 In a mixer fitted with a whisk attachment (or using a hand mixer), cream the butter. Add 1 cup of the sugar and mix. 

With the mixer running at low speed, add the room temperature eggs one at a time. Add the vanilla, greek yogurt or sour cream, and lemon zest. Working in alternating batches, and mixing after each addition, add the dry ingredients and 1/4 cup of the lemon juice to the butter mixture. 

Mix until just smooth. 

Pour into the prepared pan and bake until raised in the center and a tester inserted into the center comes out dry and almost clean (a few crumbs are OK), 55 to 60 minutes.

 Meanwhile, make the glaze: In a small bowl, stir the remaining 1/3 cup powdered sugar and the remaining 1/3 cup lemon juice until the sugar is dissolved. 

When the cake is done, let cool in the pan for 15 minutes (it will still be warm). Run a knife around the sides of the pan. 

Set a wire rack on a sheet pan with sides (to catch the glaze) and turn the cake onto the rack. Peel off the waxed paper.

 Using a turkey baster or pastry brush, spread the glaze all over the top and sides of the cake and let soak in. Repeat until the entire glaze is used up, including any glaze that has dripped through onto the sheet pan. Let cool at room temperature or wrap in plastic wrap in the refrigerator (Well wrapped, the cake will last up to a week).

Serve at room temperature in thin slices.