1 English cucumber, washed and thinly sliced (about 2 cups sliced)
1/2 cup thinly sliced red or yellow onion
In a medium bowl, whisk together sour cream (or yogurt), mustard, vinegar, milk, salt, pepper and dill until combined. Add sliced cucumbers and onions and gently stir to coat evenly. Cover and refrigerate at least 1 hour before serving.