How to Make It
In a small skillet, toast the coriander, cumin and fennel seeds over low heat, stirring frequently, until very fragrant, about 2 minutes. Transfer to a spice grinder and let cool slightly. Grind to a powder and transfer to a food processor.
Roast the red pepper and jalapeño directly over a gas flame or under the broiler, turning, until charred all over, about 10 minutes. Transfer to a large bowl, cover tightly with plastic wrap and let cool for about 15 minutes. Peel, stem and seed the red pepper and jalapeño and transfer to the bowl of the food processor with the toasted spices. Add the garlic and vinegar and pulse until the red pepper and jalapeño are finely chopped. With the machine on, drizzle in both oils. Season the harissa vinaigrette with salt and pepper.
In a small bowl, combine the crabmeat with the shallot, lemon juice and olive oil. Season with salt and pepper and toss to coat. In a large bowl, toss the lettuce and herbs with 1/2 cup of the vinaigrette and season with salt and pepper. Fold in the crab mixture. Transfer the salad to plates and serve, passing the remaining vinaigrette at the table.