Crunchy Cucumber Salad

2 English cucumbers
1 small purple onion, chopped
1/2 C sour cream
1/2 C full-fat Greek yogurt
1 T sherry vinegar or unsweetened rice wine vinegar
1 tsp granulated white sugar
4 sprigs of fresh dill, chopped
1 generous tsp capers
1/2 tsp sea salt (fine grain)
1/4 tsp white pepper
1/4 tsp granulated garlic