How to Make It
Crush the garlic to a smooth paste. In a small bowl, combine the garlic, salt and egg yolk. Slowly whisk in the oil in a thin stream to make a thick, smooth mayonnaise. Set aside.
In a bowl, crumble the saffron threads into 1 tablespoon of water. Steep for at least 10 minutes.
In a medium nonreactive saucepan, combine the tomatoes and stock. Cover and simmer gently over moderate heat for 10 minutes to blend the flavors and reduce. Puree the tomato mixture by pushing it through a coarse strainer set over a bowl. Stir in the saffron and its liquid.
Return the tomato sauce to the saucepan and bring to a simmer over moderate heat. (To make the sauce with pan juices, discard the fat from the sauté skillet, add the tomato sauce and bring to a simmer over moderate heat, whisking to dissolve the browned bits.) Off the heat, slowly whisk in the mayonnaise. Season with salt and pepper. Rewarm gently, if necessary, whisking constantly. Do not let the sauce boil or it will curdle.