Pull the rosemary leaves away from their stems and discard the stems. Keep only the tender leaves so the finished dip has no woody bits.

Finely chop the rosemary leaves and dill on a clean cutting board. The herbs should be small enough to distribute evenly through the creamy mixture.

Put the chopped herbs, mayonnaise, sour cream, pepper, onion powder, garlic powder, and salt in a small bowl. The ingredients should sit together in the bowl before mixing so the seasonings blend evenly.

Whisk the mixture firmly, or stir with a spatula, until fully combined. Stop when the dip looks smooth and evenly speckled with herbs, with no streaks of sour cream remaining.

Use a food processor instead if you prefer a more finely blended herb texture. Process only until the mixture is uniform, since overmixing can make the dip loose and overly airy.

Transfer the dip to a clean mason jar and refrigerate it with the lid on. Chilling helps the herbs and dried seasonings meld into the creamy base before serving.