Flavorful Marinated Tomatoes

Ingredients

• 1 garlic clove, minced
• 3/4 teaspoon salt
• 1/2 teaspoon pepper
• 1 teaspoon dried oregano
• 1/4 teaspoon ground mustard
• 3 tablespoons cider or red wine vinegar
• 1/2 cup olive oil
• 1/2 cup minced fresh parsley
• 4 large tomatoes, cut into 1/2-inch slices
• 1 medium sweet onion, sliced into 1/4-inch rings