Marinated Tomato Salad

serves 6

3−4 ripe heirloom tomatoes
1 small yellow onion, thinly sliced
1 Tbsp Dijon or whole grain mustard
1 tsp coarse sea salt
1 tsp ground black pepper
Fresh flat leaf parsley, chopped
Fresh tarragon, chopped
Fresh basil, cut into ribbons
3 Tbsp red wine vinegar
4 Tbsp olive oil

Slice tomatoes into half-inch rounds and arrange in a single layer in a shallow dish with sliced onions. Whisk together remaining ingredients and pour over tomatoes. Chill and marinate at least one hour before serving. Serve with crusty bread.