Savory Tomato Butter
["1/4 c. minced onion", "1/2 c. (1 stick) plus 2 tsp. unsalted butter", "3 c. peeled and seeded tomatoes, pureed"]
["Saute the onion over medium heat in the 2 teaspoons of butter until it just begins to color, 3 to 4 minutes.", "Add the tomato puree; bring to a boil.", "Turn the heat down to a simmer; cook for about 5 minutes.", "Strain the mixture through a fine strainer, pressing to get out most of the liquid.", "Put the liquid in a clean saucepan.", "Bring to a boil over medium-low heat and cook, stirring occasionally, until reduced to 2 or 3 tablespoons, about 30 minutes.", "During the last 10 minutes or so, take care to keep it from scorching.", "Let it cool.", "Beat the reduction into the remaining butter.", "Refrigerate until ready to use.", "Makes about 3/4 cup."]
["onion", "unsalted butter", "tomatoes"]