Preheat oven to 350°F. Butter an 8-inch x 4-inch loaf pan and line with a parchment paper sling.
In a small bowl, whisk together flour and baking powder. Set aside.
In a large mixing bowl, either using an electric hand mixer or a stand mixer with whisk attachment, beat the eggs, sugar and salt until thickened and pale, 2-3 minutes at medium-high speed.
Beat in yogurt, lemon zest, lemon juice and vanilla for another 2 minutes.
Add the dry ingredients and mix on low speed until just combined, scraping down bowl as needed. Slowly mix in 6 tablespoons melted butter and poppy seeds until well combined. Transfer to prepared pan and smooth top.
Bake 55-60 minutes, or until top is golden brown and a toothpick inserted into the center comes out clean. Let cool in pan for 10 minutes, then carefully lift cake out of pan using the parchment paper sling.
To make the glaze, whisk together powdered sugar and lemon juice in a small bowl until smooth. Pour over the top of the cake, letting it drip down the sides. Cool completely before slicing.