Grilled Steak Sandwiches with Marinated Watercress, Onion, and Tomato Salad

Ingredients

• 1 2-pound well-trimmed tri-tip beef roast
• 1 tablespoon dark brown sugar
• 1 bunch watercress
• 1 ¾ teaspoons dry mustard
• 6 tablespoons white balsamic vinegar
• ½ cup olive oil
• 6 5-inch pieces French baguette
• + 2 more ingredients
• • ½ white onion
  • 4 large plum tomatoes

Prepare barbecue (medium-high heat). Whisk oil, vinegar, and 3/4 teaspoon mustard in large bowl. Season dressing with salt and pepper. Transfer 2 tablespoons dressing to small bowl; whisk in sugar and 1 teaspoon mustard. Sprinkle beef all over with salt and pepper, then top with mixture from smal...

View full recipe at Epicurious