5 tablespoons plus 1 teaspoon unsalted butter, softened, plus more for pan
1/2 pint strawberries and ½ cup raspberries, quartered and mashed
½ cup yogurt
1 tablespoon tarragon chopped finely
1 3/4 cups all-purpose flour
1 teaspoon baking soda
1/2 teaspoon ground cinnamon
1/4 teaspoon baking powder
1/4 teaspoon salt
1 cup sugar
2 large eggs
½ cup milk
Preheat oven to 350 degrees. Butter an 8-by-4-inch loaf pan.
In a small saucepan, bring strawberries and raspberries to a boil over medium heat. Cook, stirring, 1 minute. Add chopped tarragon and set aside.
In a medium bowl, whisk together flour, baking soda, cinnamon, baking powder, and salt; set aside.
With an electric mixer, cream butter, sugar, and eggs in a mixing bowl until light and fluffy. Add yogurt.
Add flour mixture alternately with 1/3 cup milk, beginning and ending with flour. Fold in reserved strawberries and raspberries.
Scrape batter into prepared pan, smoothing top.
Bake until a toothpick inserted in center comes out clean, about 1 hour (tent with foil after 45 minutes if top is getting too dark). Cool in pan 10 minutes.