In a large, heavy bottom skillet, heat the vegetable oil over high heat.
Add corn and red onion and cook, until corn is slightly charred, about 5-7 minutes. Turn heat to low and add garlic, and jalapeno and cook for 1 minute longer. Remove from heat and allow to cool to room temperature.
In a large mixing bowl, mix together the cooled corn, cut tomatoes, and radishes.
In a small mixing bowl, whisk together all the dressing ingredients.
Add dressing to corn mixture and gently fold. Sprinkle the top of salad with cojita, pepitas, and cilantro. Serve.