With their thin, fragrant skins and low acidity, Meyer lemons are worth the splurge. This relish uses the whole fruit, which gets mellowed out by sauteed sweet fennel and onion. Serve alongside our Juniper-and-Gin Gravlax.
Cut lemons lengthwise into eighths; remove seeds. Thinly slice crosswise into pieces (you should have about 1 1/2 cups).
Heat oil in a large skillet over medium-high until shimmering. Add fennel, onion, fennel seeds, and a large pinch of salt. Reduce heat to medium; cook, stirring occasionally, until mixture is softened and just beginning to turn golden, 10 to 12 minutes. Add lemons, honey, and 1/3 cup water. Increase heat to high and bring to a boil; cook until reduced to a jammy consistency and liquid is almost completely evaporated, 4 to 5 minutes more. Transfer to a bowl; let cool completely. Refrigerate in an airtight container up to 5 days.