Preheat the oven to 200°F and line a baking sheet with parchment paper.
Wash and dry the lemon. Zest only the yellow outer layer, avoiding the bitter white pith.
Spread the zest in a thin layer on the prepared baking sheet.
Dry for 45 to 60 minutes, watching carefully near the end.
Remove the zest when it is completely dry and brittle. Allow it to cool completely.
Crush the dried thyme briefly in a food processor, spice grinder or mortar and pestle.
Combine 1/2 teaspoon dried lemon zest, the thyme and the salt.
Transfer to a clean, dry airtight jar. Label and date the jar.