Preheat oven to 225°. Remove peels in strips from lemons (or oranges or clementines) using a vegetable peeler. Place peels, pith sides up, in a single layer on a parchment paper-lined jelly-roll pan. Bake 1 hour and 30 minutes to 1 hour and 45 minutes or until dried and fragrant; cool completely. Grind to a coarse powder in a spice grinder or mortar and pestle. Stir together 2 Tbsp. ground roasted citrus peels, kosher salt, and freshly ground black pepper in a small bowl. Store in an airtight container up to 2 months. Use to season fish, meat, or vegetables before, during, or after cooking.