From Dr. Weil
2 tablespoons balsamic vinegar
2 tablespoons freshly squeezed lemon juice
1/2 teaspoon grated lemon zest
1/2 teaspoon sea salt
1/2 teaspoon freshly ground black pepper
1/4 cup extra-virgin olive oil
Put the balsamic vinegar, lemon juice, lemon zest, salt, pepper, in a small bowl and stir to combine. Slowly pour in the olive oil, whisking all the while, and continue whisking until smooth.
Transfer to a small container with a fitted lid and shake well.