How to Make It
Cook noodles according to package directions, omitting salt and fat. Drain; toss with butter, cover, and set aside.
Combine grated onion, panko, milk, dill, 1/2 teaspoon pepper, 1/4 teaspoon salt, allspice, and nutmeg in a large bowl; stir to moisten panko. Add beef; stir with your hands until combined. Gently form beef mixture into 20 balls (about 1 tablespoon each).
Heat a large skillet over medium-high heat. Coat pan with cooking spray. Add meatballs to pan; cook 6 minutes, turning occasionally, or just until cooked through (thermometer inserted into center of a meatball should register 160°). Transfer meatballs to a paper towel-lined plate; leave browned bits in pan.
Place flour in a medium bowl; gradually whisk in stock. Return pan to medium heat; add stock mixture and jelly to pan. Cook 2 minutes or until thickened and bubbly, stirring constantly with a whisk. Remove pan from heat; whisk in sour cream, remaining 1/2 teaspoon pepper, and remaining 1/2 teaspoon salt. Serve meatballs and sauce with noodles.