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 2 popcorn kernels, then put the lid on the pot and place the pot on medium to high heat.
Listen for the two kernels to pop, then 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 popping to start again.
Sprinkle salt and pepper over the popcorn and use a fine grater or a microplane to grate the lemon zest. Toss the popcorn to make sure all the flavorings are distributed, then serve in a bowl.