Prepare the tomatoes by dropping them into boiling water for about a minute, or until the skins begin to crack.
Transfer them to an ice bath, then peel away the skins. Purée the peeled tomatoes in a high-speed blender or food processor until completely smooth. You should have about 5 cups (1200 ml) of purée.
Add the chopped cucumber and onion to the blender or food processor and purée until smooth. If your blender is struggling, add a bit of the tomato purée to help it along.
Pour the mixture into a large bowl, stir in the sour cream, and season with salt, ginger, pepper, lemon juice, and lemon rind.
Mix until well combined.
Prepare the melon by cutting the cantaloupe in half and scooping out the seeds. Use a melon baller to create small spheres, or simply peel the cantaloupe and cut it into bite-sized chunks.
In a separate bowl, gently toss the melon pieces with the fresh or dried basil.
Cover both the soup and the melon mixture and chill them in the refrigerator for at least 2-3 hours, or until thoroughly cold.
To serve, ladle the chilled soup into pre-chilled bowls.
Top each serving with a generous spoonful of the basil-infused cantaloupe and enjoy immediately.
