How to Make It
Roast the red pepper and jalapeño directly over a gas flame or under a preheated broiler, turning, until charred all over. Transfer the red pepper and jalapeño to a large bowl, cover tightly with plastic and let cool for 15 minutes. Peel, seed and stem the red pepper and jalapeño, then cut them into 1/4-inch dice.
In a large bowl, mix half of the red pepper with half of the jalapeño; reserve the rest for another use. Add the cheese, mayonnaise, sour cream, cilantro, lemon juice and cayenne to the bowl and mix well; season with salt and pepper. Chill for at least 2 hours.
In a medium cast-iron skillet, heat the oil. Add the andouille and cook over moderate heat, stirring, until the fat is rendered and the sausage is crispy, 8 minutes. Add the onion and cook, stirring, until translucent, 3 minutes. Stir in the green pepper and garlic and cook, stirring, until the garlic is fragrant, 2 minutes. Sprinkle in the flour and stir until incorporated; add the tomato and cook over moderately low heat, stirring, until it starts to break down, 3 minutes. Add the stock and bring to a simmer; cook until the gravy is thick enough to coat the back of a spoon, 5 minutes. Stir in the scallions and season with salt.
Preheat the oven to 450°. Spread the french fries on a heatproof serving platter. Spoon the gravy all over the fries and top with the crayfish. Dollop 1 cup of the pimento cheese all over the fries; reserve the rest for another use. Bake the poutine for about 5 minutes, until the cheese is bubbly and melted. Serve immediately.