How to Make It
In a mortar, using a pestle, finely grind the walnuts with the coriander, sesame and nutmeg. Season the dukka with salt.
In a large saucepan, heat the 3 tablespoons of olive oil. Add the onion and cook over moderate heat, stirring, until lightly browned, about 10 minutes. Stir in the spinach in large handfuls, letting each wilt slightly before adding more, 5 to 7 minutes. Season with salt and pepper.
Meanwhile, light a grill or preheat a grill pan. Brush the baguette slices with olive oil and grill over high heat, turning, until lightly charred, 2 to 4 minutes. Transfer to a platter.
In a medium bowl, toss the arugula with the lemon juice and season with salt and pepper. Top the baguette slices with the spinach and arugula, sprinkle with the dukka and serve.