1 red onion, julienne
2 Tbsp. sumac
1 tsp. kosher salt
2 tsp. sugar
1 Tbsp. red verjus
1 small seedless watermelon, sliced 1½-inch thick
4 French breakfast radishes, shaved for garnish
Preheat the grill to medium-high heat.
In a bowl, add red onion, sumac, salt, sugar and verjus. Let marinate for 30 minutes at room temperature.
Brush the watermelon slices with olive oil on both sides. Place the watermelon on the grill and cook for 1 minute. Rotate the watermelon 90 degrees and cook 1 minute more. Flip the watermelon and cook for 1 minute.
Remove from heat and sprinkle with grey salt. Garnish with red onion mixture and shaved radishes.