Peel the thin skin from the bottarga. Finely grate. Set aside.
Dissolve the saffron in 3/4 cup of boiled water.
Bring a large pot of salted water to a boil. Cook the spaghetti until al dente (2 minutes less than the package recommends). Drain, retaining some of the cooking water.
Meanwhile, in a large skillet over medium heat, warm the olive oil. Add the spaghetti and then the saffron water. When evenly distributed, add the bottarga. Add some retained cooking water. Mix well until creamy, and serve immediately.