Preheat the oven to 350°. Line an 8½x4½" loaf pan with parchment paper, leaving an overhang on the long sides, and lightly coat with nonstick spray.
Whisk flour, baking powder, and salt in a medium bowl, and set aside.
Using a stand mixer, work the lemon zest into the sugar until sugar starts to clump and the mixture is very fragrant about 1 minute. Add eggs
Add eggs, oil, and vanilla and beat with the mixer on high speed until light and thick, about 4 minutes.
Reduce speed to low and mix in half of the dry ingredients, then mix in the yogurt. Mix in remaining dry ingredients followed by 5 Tbsp. lemon juice and poppyseeds.
Scrape batter into prepared pan and smooth top.
Bake until the top is golden brown and a tester inserted into the center comes out clean, 50–60 minutes.
Transfer pan to a wire rack. Poke holes in the top of the loaf and brush the remaining 4 Tbsp. lemon juice over top.
Let sit 15 minutes, then run a knife around the sides to loosen and use parchment paper to lift the loaf lifts out of the pan and onto the rack. Remove parchment and let cool completely.
