In the work bowl of a food processor, combine chopped tomatoes, watermelon, and celery; process for 1 minute. Place a fine-mesh sieve over a large bowl. Strain vegetable mixture, pressing to release juices; discard solids. Measure 4½ cups vegetable juice; reserve any remaining juice for another use.
In a large bowl, place ½ cup vegetable juice. Sprinkle gelatin over juice, and let stand.
In a small pot, bring vinegar, hot sauce, salt, brown sugar, lemon juice, and remaining 4 cups vegetable juice to a simmer over medium heat. Pour over gelatin mixture; whisk until gelatin is fully dissolved.
In an 8×4-inch metal loaf pan, arrange 2 tomato slices, a few cherry tomato halves, and a few basil leaves. Pour enough gelatin mixture over vegetables to barely cover. (You may need to push tomatoes down into gelatin mixture once poured.) Refrigerate for 1 hour.
Arrange remaining tomatoes and remaining basil over set mixture. Pour remaining gelatin mixture over tomatoes. Refrigerate until fully set, about 4 hours.
To remove, dip mold in warm water for a few seconds. Invert onto a serving platter. Garnish with tomatoes and basil, if desired. Cover and refrigerate until ready to serve. Slice and serve with Horseradish Sour Cream.
Horseradish Sour Cream
In a small bowl, stir together all ingredients until smooth. Refrigerate until ready to serve.
Notes
KITCHEN TIP: Serve a slice of aspic on toasted bread with a light slathering of mayo, fresh cracked pepper, and additional fresh basil leaves. Trust us, it’s likely to be the best tomato sandwich you’ve ever made.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/fresh-tomato-aspic/