Preheat oven to 350* F. Prepare an 8/4 loaf pan by greasing it with coconut oil and lining with a parchment sling for easy removal- see photos for reference.
In a small bowl, combine vegan yogurt, milk, lemon juice and vanilla. Stir to combine and set aside.
In another small bowl, combine flour, baking powder, baking soda and salt. Stir to combine and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream vegan butter, sugar and lemon zest together until it is well combined and fluffy.
Into the mixer add half of the milk and yogurt mixture. Mix on low to combine and scrape the bowl down.
Now add half of the flour mixture and mix on low until just combined. Scrape the sides of the bowl down.
Next add the remaining liquid mixture and mix on low again until just combined. Scrape the sides of the bowl down.
Add the poppy seeds and the remaining dry mixture to the bowl. Mix until just combined.
Remove the bowl from the mixer and use a spatula to scrape the bowl down and fold the mixture a couple of times to ensure everything is homogenous.
Scrape batter into prepared 8x4 loaf pan, smoothing the top out with the back of the spatula.
Bake in a 350* oven for 50-55 minutes turning the loaf halfway through. Test for doneness by inserting a toothpick into the center of the loaf. Its done when it comes out clean.