Artichoke and Pea Gratin

Ingredients

• 1 tablespoon butter
• 1 tablespoon flour
• 1 1/4 cup low fat milk
• 1 9 ounce bag frozen artichoke hearts thawed
• 1 cup frozen peas thawed
• 1/2 teaspoon salt
• 1/2 teaspoon lemon zest
• parmesan cheese grated