Watercress-Walnut Pesto

Ingredients (8)

• 1 bunch (about 2 1/2 ounces, including the stems) watercress
• 5 tablespoons freshly squeezed lemon juice
• 2 tablespoons balsamic vinegar
• 1/2 cup grated Parmesan cheese
• 1/2 cup walnut pieces
• 1/2 cup extra-virgin olive oil
• 4 garlic cloves, peeled but whole
• 1 teaspoon kosher salt