Prepare the dressing by whisking the lime juice, extra virgin olive oil, salt, and black pepper in a small bowl until emulsified.
In a large mixing bowl, combine the diced red onion, halved cherry tomatoes, and minced serrano pepper.
Add the cubed avocado and chopped cilantro to the bowl.
Drizzle the lime dressing over the vegetable mixture.
Using a large spoon or silicone spatula, gently toss the ingredients until evenly coated, ensuring the avocado cubes remain intact and do not mash.
Serve immediately at room temperature or slightly chilled.