Prepare all vegetables: Halve the cherry tomatoes, dice the cucumber, thinly slice the red onion, and ensure the corn kernels are ready.

In a large mixing bowl, gently combine the prepared cherry tomatoes, cucumber, corn kernels, and red onion.

Prepare the vinaigrette: In a small bowl or jar, whisk together the olive oil, lemon juice, Dijon mustard, salt, and pepper until emulsified.

Pour the vinaigrette over the vegetable mixture. Toss gently until all components are lightly coated. Ensure not to over-mix to keep the vegetables crisp.

Fold in the chiffonade of fresh basil just before serving to maintain its bright color and aroma.

Chill for at least 15 minutes before serving to allow the flavors to meld, but serving closer to room temperature often enhances the sweetness of the corn and tomatoes.