To create an emulsified dressing (one that does not separate) slowly whisk in the oil a few drops at a time to start. Gradually increase the amount of oil in a thin stream until all oil is incorporated. Alternatively, you may place all ingredients in a mason jar and shake before using.
3/4 cup olive oil
1/4 cup grapefruit juice (approx. 1/2 of a grapefruit), or other citrus may be used
2 Tbsp shallot, minced (approx. 1 shallot)
2 Tbsp white wine vinegar
1 tsp kosher salt
1/2 tsp grapefruit zest
1/4 tsp freshly ground black pepper
Combine all ingredients in a small mason jar. Shake to combine. Toss into salad before serving.