It's very important the ingredients for this cake are room temperature - make sure to take out your eggs and butter a few hours before using; you can always take fridge temperature eggs and put them in warm water for 10-15 minutes for a quicker way of getting eggs to room temperature. You can also pop the milk in the microwave before adding to get it to room temp.
Preheat the oven to 350F (176C).
Add the room temp, softened butter and sugar to the bowl of a stand mixer. Beat together using the paddle attachment until the mixture is light in color and looks fluffy, about 5 minutes. Make sure to scrape down the sides and bottom of the bowl a few times while it is mixing to incorporate everything.
Mix the dry ingredients - flour, baking powder, and salt - together in a separate bowl.
Measure out the milk and combine with vanilla extract. Measure out the lemon juice separately. Zest the lemons and set aside the zest until ready to use.
Prepare the bundt cake pan (we use a 10 cup bundt pan) by using a vegetable oil-based spray, vegetable shortening, or brushing the inside with vegetable oil. Try to avoid using butter, as it can sometimes cause more sticking.
Starting with the first three eggs, add one egg at a time to the mixer with the butter and sugar mixture; let each egg fully mix in before adding the next one.
Before adding the 4th egg, add in about 2 tablespoons of the flour mixture and mix until combined; this will help stop the batter from splitting.
Add the 4th egg and mix until fully incorporated, then add another 2 tbsp of flour. Add the 5th egg, then 2 more tbsp of flour, and add the 6th egg, mixing between each addition of ingredients. If you do have a little bit of splitting/curdling occurring at this stage, don't worry too much!
Once all the eggs have been added, add in about one-third of the rest of the flour mixture and mix until just combined (at this stage, we are also trying to avoid overmixing).
Add in half of the milk and vanilla mixture and mix until just combined; then add another 1/3 of the flour mixture, and again mix until just combined. Add in the remaining half of the milk + vanilla and mix until just combined. Make sure to scrape the sides and bottom of the mixing bowl as well to make sure everything is incorporated.
Add in the lemon zest and the lemon juice and mix until just combined.
Now add the last third of the flour, and mix until just combined; the batter should be smooth and not curdled or split at this stage; if it looks really split, you can try adding flour one tablespoon at a time until the batter smooths out a little bit.
Spoon the batter into the bundt pan and smooth out the top so it is even.
Bake the cake on the center rack for 40-50 minutes, checking whether the top is getting too dark throughout. If it gets brown very quickly, cover with foil. When it's ready, a cake tester inserted in the cake should come out clean!
Remove the cake from the oven and let it cool for about 15-20 minutes before handling. Loosen any edges you can with a spatula, carefully. Turn the cake out onto a cooling rack; if it doesn't release immediately, let it sit for 10 more minutes and remove from the pan.
Let the cake cool completely; when it is cool, prepare the glaze for the top by combining powdered sugar and lemon juice as needed to create a thick yet pourable glaze.
If you need to, you can trim the bottom of the cake for it to sit flat on your cake stand/plate.
Pour or spoon the icing over the cake and garnish with lemon zest, candied lemon slices, or candied lemon peel! Enjoy this beautiful showstopping cake for any spring occasion!