Vegetable Spinach Salad

8 ounces fresh mushrooms, quartered
1/4 - 1/2 of a red onion, sliced and separated into rings
1 pint cherry tomatoes, halved
1 large bag fresh spinach leaves
8 ounce ball of fresh mozzarella, cut into bite size pieces
freshly ground black pepper

Mustard Tarragon Vinaigrette

3 tbl red wine vinegar
1 tbl Dijon mustard
1/2 tbl dried tarragon
2 tbl olive oil

Whisk everything together until smooth. Pour over salad and enjoy.