Preheat the oven to 350°F (180°C). In a large mixing bowl, whisk together the flour, baking powder, baking soda, salt, and poppy seeds. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or a large mixing bowl using a hand-held mixer, beat the butter and sugar until light and fluffy.
Mix in the eggs one a time, then mix in the vanilla. Slowly mix in the lemon juice, lemon zest, and oil.
Alternate mixing the flour mixture and the sour cream into the wet ingredients, starting with the flour and ending with the flour. Mix until just combined.
Spray a 10-inch bundt pan well with non stick cooking spray. Pour the batter into the prepared bundt pan and evenly spread it around.
Bake at 350°F for 45-55 minutes or until a toothpick inserted into the cake comes out clean. Cover loosely with foil if needed for the last 5-10 minutes of baking to prevent excess browning.
Remove from the oven and cool in the pan on a wire rack for 30 minutes. Then invert the cake onto a wire rack to finish cooling.