In a mason jar, combine fresh basil, lemon juice, olive oil, salt, and pepper. Seal the jar tightly and shake vigorously until the ingredients are fully emulsified.

Bring a large pot of salted water to a rolling boil. Once boiling, add the sweet corn and cook for 3 to 5 minutes. Transfer the corn to a bowl filled with ice water.

Remove the corn from the ice water, pat dry, and cut the kernels off the cob. Place the kernels in a large mixing bowl.

Rinse and chop the tomatoes into bite-sized pieces. Dice the avocado and add both to the bowl with the corn.

Finely chop the red onion and add it to the bowl. Toss the salad gently.

Shake the dressing to re-emulsify. Drizzle it over the salad and toss gently to coat.

Serve immediately in a serving dish or the mixing bowl, garnished with fresh basil leaves.