If using fresh lemons, zest 4-5 medium lemons to yield about 60 ml of zest.
Spread the zest on a baking tray lined with baking parchment and leave to air-dry for 1-2 days until brittle, or dry in the oven at 65 °C for 30-60 minutes, checking until completely dry and crumbly.
Add the dried lemon zest, whole black peppercorns, garlic powder, onion powder and fine sea salt to a spice grinder or small food processor.
Pulse until you reach your desired consistency, stopping before the mixture becomes pasty.
Transfer the seasoning to an airtight jar and store in a cool, dark cupboard for up to 6 months.