Using a mandoline, thinly slice cucumber and red onion. To slice red onion, cut the onion in half and peel outermost layers. Slice the onion using the mandoline. Break up onion slices with your hands.
In a large mixing bowl, whisk together the vegan mayo, vegan yogurt, garlic, lemon juice, apple cider vinegar, mustard, maple syrup, salt, and pepper. Taste and adjust seasonings if needed.
Add sliced onions, cucumber, capers, and dill. Mix together.
Serve immediately or refrigerate before enjoying.
Video
Notes
Leftovers will keep well in the fridge for 3 days.