Raspberry Pound Cake

FOR THE RASPBERRY FILLING: Stir cornstarch and water together in bowl; set aside. Cook raspberries, sugar, and salt in small saucepan over medium heat, stirring occasionally, until slightly thickened and mixture measures 1 scant cup, 8 to 10 minutes.

 Stir cornstarch mixture to recombine, then stir into raspberry sauce. Cook until thickened, about 1 minute. Transfer filling to bowl and refrigerate, uncovered, until no longer warm, about 1 hour. (Filling can be covered and refrigerated for up to 2 days.)

FOR THE POUND CAKE: Adjust oven rack to lower-middle position and heat oven to 300 degrees. Grease and flour 9 by 5-inch loaf pan. Whisk eggs and vanilla together in 2-cup liquid measuring cup. Whisk flour, salt, and baking powder together in bowl. Whisk sour cream and milk together in second bowl.

 Using stand mixer fitted with paddle, beat butter, sugar, and lemon zest on medium-high speed until pale and fluffy, 5 to 7 minutes, scraping down bowl as needed.

 Reduce speed to medium and gradually add egg mixture in slow, steady stream. Scrape down bowl and continue to mix on medium speed until uniform, about 1 minute longer (batter may look slightly curdled).

 Reduce speed to low and add flour mixture in 3 additions, alternating with sour cream mixture in 2 additions, scraping down bowl as needed. Give batter final stir by hand.

 Transfer half of batter (about 2 cups) to prepared pan. Stir raspberry filling to loosen. Spoon half of raspberry filling over length of batter in pan, leaving ½ inch border. Using butter knife, thoroughly swirl filling throughout batter, taking care to not leave any big deposits of filling in center or along sides of pan.

 Transfer remaining batter to pan and repeat spooning and swirling with remaining raspberry filling. Tap pan on counter twice to release air bubbles.

Bake until toothpick inserted 1 inch to side of split in center of cake comes out clean (very top center of cake may seem underdone; this is OK), 1 hour 15 minutes to 1 hour 35 minutes, rotating pan halfway through baking.

 Run thin knife around edges of pan. Let cake cool in pan on wire rack for 15 minutes. Remove cake from pan and let cool completely on rack, about 2 hours. Slice and serve. (Cooled cake can be wrapped tightly in plastic wrap and stored at room temperature for up to 3 days or frozen for up to 1 month.)