Rinse chili peppers under running water and dry them completely with a paper towel. Remove crowns and split them from the top lengthwise into halves then cut them into 1-inch pieces.

Rinse the lemon and slice them into thin circles. Cut each round slice into four quarters.

Meanwhile, combine split mustard seeds, salt, and turmeric in a medium glass bowl. Heat 3 tablespoons of hot oil in a skillet then transfer hot oil into the mustard mixture in a bowl. Cover the bowl with a lid and let the mixture rest for 10 minutes.

Spread the chilies on a paper towel. Use another paper towel to dry all the moisture from the chilies.

Transfer the chilies and lemon wedges into the bowl with oil and mustard mixture. Stir everything well until well combined.

Transfer the chili pickle into an airtight jar. Let it sit at room temperature for 2 days then transfer the jar to the refrigerator.