Spaghetti with cod roe たらこスパゲティ

The night after making "julienned potato with spicy cod roe", we decided to make this classic Japanese pasta dish. Reportedly, it was invented in a small pasta restaurant called "hole in the wall" or 壁の穴 in Shibuya, Tokyo around 1967. (Now this restaurant has expanded into a company running multiple Italian and noodle restaurants). The original recipe was supposedly made with softened butter and lemon juice mixed with cod roe.  This was placed in the bottom of a pasta plate. Hot pasta was mixed in and finished with a garnish of nori. This dish appears to have started an entire genre of Japanases-style pastas 和風パスタ. This dish has become a favorite home cooking dish and many variations have developed. I am not sure how we came up with our own variation but I have a feeling that caramelized onion may have been my wife's idea.

My wife does not particularly care for spaghetti, which I suspect, is possibly due to the childhood "trauma" of eating canned spaghetti which many children face in the U.S. So instead of spaghetti, we use udon noodles (dried thin variety such as "sanuki" 讃岐 or "inaniwa" 稲庭) which has a nice firm texture. For us, we need only two small servings (as a last starch dish). So, we use one serving or bundle of dried udon noodles (cooked as per the package instruction) and one large sac of cod roe or tarako. After removing the roe from the sac, I mix in a small amount of lemon juice and sake to make it a smoother consistency. Meanwhile, in olive oil, I saute and caramelize one small onion cut into thin strips (this may take 10-15 minutes). I do not add salt since the tarako can be salty. I add the cooked noodles to the onions and continue sauteing to warm up the noodles. I then add the tarako mixture and remove from the heat. Mix well so that all the noodles are coated with tarako which turns white from the heat of the noodles. Taste and if needed, add salt. Plate, and garnish with thin strips of nori, perilla, and freshly cracked back pepper. Squeeze lemon on the pasta just before serving.