Prepare the garlic scapes by blanching them briefly in boiling salted water for 1 minute. Immediately transfer them to an ice bath to stop the cooking process and retain their bright green color. Drain well and pat dry.

Combine the blanched garlic scapes, fresh dill, chopped yellow onion, apple cider vinegar, salt, pepper, and sugar in a food processor.

Pulse the mixture in the food processor until it reaches a coarse, relish-like consistency. Do not over-process; you want some texture remaining, not a smooth paste.

Taste the relish and adjust seasoning as necessary. Add a pinch more salt or sugar if desired, or a splash more vinegar for tanginess.

Transfer the relish to a clean, airtight jar. Allow it to sit in the refrigerator for at least 2 hours before serving to let the flavors meld together.

Serve chilled as a topping for grilled fish, sausages, soft cheeses, or mixed into mayonnaise or yogurt for a vibrant dip.