Line a sheet tray with aluminum foil. Arrange the fries on the sheet tray in a single layer. Bake according to the package instructions. Season with salt.
Heat the olive oil in a large cast-iron pan over medium heat. Add the onion and cook until softened, about 5 minutes. Add the garlic, chili powder and cumin and cook until the spices are fragrant, 1 to 2 minutes. Add the beef, salt and a few grinds of black pepper and cook, breaking the beef into bits while browning, until fully cooked, 8 to 10 minutes. Add the marinara sauce and stir to coat. Let cook for 5 minutes to let the flavors meld.
Heat the nacho cheese sauce according to the package instructions. Top the fries with the chili and nacho cheese sauce, then garnish with the scallions and pickled jalapenos.