In a medium to large cast iron pot with a lid (Dutch Oven), pour in the oil; it should cover the bottom of the pot. Add in 2 popcorn kernels. Place the lid on the pot, then place the pot on medium to high heat.
When the two kernels pop, immediately add in the rest of the kernels. They should cover the bottom of the pot in a single layer. Replace the lid again and listen for when the kernels start to pop. Move the lid slightly over so that it has a crack for the steam to escape, then listen for the popping to slow down. Turn off the heat and let the last few kernels pop.
Sprinkle the salt and pepper over the popcorn and use a fine grater or a microplane to grate over the lemon zest. Toss it to make sure all the flavorings are distributed around the popcorn, then serve in a bowl.