In a mixing bowl whisk together flour, poppy seeds, baking powder, baking soda and salt for 30 seconds.
In a separate large mixing bowl, using an electric hand mixer set on medium-high speed, whip together sugar, butter, lemon zest and 1 Tbsp canola oil until pale and fluffy. Mix in remaining 3 Tbsp canola oil. Blend in eggs one at a time mixing until combined after each addition. Blend in egg yolk and vanilla extract.
In a 2 cup liquid measuring cup (used to measure milk), whisk together the milk, sour cream and 3 Tbsp lemon juice.
Using a rubber spatula and working in three separate batches, beginning and ending with flour mixture, add 1/3 of the flour mixture alternating with half of the milk mixture and fold just until combined after each addition.
Divide batter among 12 - 15 muffin cups**, filling each to the top and bake in preheated oven 15 - 18 minutes until toothpick inserted into center comes out clean.
Cool in muffin tin several minutes then transfer to a wire rack to cool slightly. Drizzle tops with glaze while still warm. Store in an airtight container at room temperature.
For the glaze:
In a bowl, whisk together powdered sugar and 2 Tbsp lemon juice until well blended.
**I did 12 because I like big muffin tops, but the muffins slightly touched each other on the sides so with that said if that would bother you just make more and don't fill them so heaping full.