Melt remaining 6 tablespoons butter in a large saucepan over medium heat. While butter is bubbling, add flour. Cook, stiring constantly with a wire whisk, for 1 minute . While whisking, slowly pour in milk. Continue cooking, whisking constantly, until mixture bubbles and becomes thick. Remove from heat, and stir in cream, lemon juice, and remaining 2 teaspoons salt and 1/4 teaspoon pepper.