1teaspoonchopped fresh tarragon leaves plus more for garnish
kosher salt and freshly ground black pepper
Place spinach, strawberries, blueberries, red onion and tuna in a bowl. In a small bowl or a jar with a lid, mix extra virgin olive oil and grainy mustard together. Add rice wine vinegar, sugar, kosher salt and pepper and chopped tarragon leaves and mix well until emulsified. Dress salad and garnish with more whole tarragon leaves if desired.