Preheat oven to 450F.

In a small skillet, toast sesame seeds over medium heat, stirring constantly, for about 3 minutes or until golden but not browned. 

Pour Mexico City sauce in a blender and add the toasted sesame seeds along with the broth, cilantro, and hoja santa or fennel fronds. Blend until sauce is smooth, about a minute. 

Pour sauce in a medium saucepan, bring to a boil and reduce heat to just simmer. Cover and let cook for 5 minutes. Season with salt to taste and keep warm.

Season salmon with salt and pepper. Coat a large non-stick baking sheet with olive oil. Place salmon on baking sheet. Bake until salmon is cooked through, about 12 minutes for medium-rare. 

Place salmon in a plate and ladle 3 to 4 tablespoons of the Green Pipian sauce over the fish. Garnish with some toasted sesame seeds and a few cilantro leaves. Provecho!