Prepare the Fries: Cook the French fries according to package directions until golden and crispy. Season with salt.
Make the Corn Relish: Heat olive oil in a skillet over medium-high heat. Add corn and cook until lightly charred, about 3–4 minutes. Add red pepper and onion and sauté for 2 more minutes. Season with salt and pepper. Remove from heat.
Mix the Crema: In a small bowl, stir together the sour cream (or yogurt), lime juice, chopped cilantro, and salt. Adjust flavor to taste.
Assemble the Fries: Place fries on a serving plate. Top with warm corn relish, drizzle with crema, and sprinkle with cotija cheese. Garnish with extra cilantro and a squeeze of lime if desired.