1/4 cup finely chopped red onion
2 tablespoons prepared horseradish
1/2 cup ketchup
1 cup halved cherry tomatoes
1 tablespoon fresh lemon juice
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
Combine all ingredients in a blender or a small food processor and pulse just until well incorporated, scraping down the inside of the container if needed. Chill before serving.
Note: Nutritional analysis is per 1/4-cup serving.