Summer Fruit Cookies

From kingarthurbaking.com

1 stick butter, cold
2/3 cup granulated sugar
1/2 teaspoon sea salt
zest of 1 lemon
1 large egg
1 teaspoon vanilla extract
1 1/2 cups unbleached all-purpose flour
1 teaspoon baking powder
1 cup fresh fruit, chopped if using strawberries, peaches, cherries, etc. All one fruit or a combination. (We used raspberries and strawberries.)
Topping
2 tablespoons turbinado sugar

1. Heat the oven to 350°F. Line two baking sheets with parchment paper or silicone pads.  
2. In the bowl of a stand mixer fitted with the flat beater attachment or working in a large mixing bowl with an electric hand mixer, beat the butter, sugar, salt, and lemon zest until smooth, 2 to 3 minutes on medium speed. Scrape the bowl, then beat in the egg and vanilla. 
3. Add the flour and baking powder and mix well. Scrape the bowl and mix again briefly. 
4. Add the fruit and mix on low speed just until the fruit is evenly distributed and beginning to break down. Be careful not to overmix or the dough will become pastel-colored instead of streaked with bright fruit color. 
5. Drop heaping tablespoons of dough onto the sheets about 2 inches apart. Sprinkle with turbinado sugar. Refrigerate cookies for about 10 minutes. 
6. Bake for 15 to 20 minutes, until the middles are set and the edges are browned. 
7. Remove the cookies from the oven and let them cool right on the pan; serve warm or at room temperature. Makes about 16 cookies.