First thinly slice a red onion and cover completely with rice wine vinegar. Let sit for at least 1 hour or overnight.
Next, I actually cut the round watermelon into a square/rectangle, trimming off the outer rind and then the white rind corners if necessary. Slice the watermelon flesh into 4 thick slices and then each slice in half, then each half cut on the diagonal. You should have 16 triangles when finished.
In a small bowl toss the arugula with the olive oil, salt and black pepper.
To plate, add some dressed arugula salad greens, lay four watermelon triangles as shown or as you like.
Sprinkle some of the pickled red onions, a drizzle of balsamic syrup and crumbles of goat cheese. Top it all off with some freshly cracked black pepper and fresh thyme leaves. Serve chilled.