Cook spaghetti to al dente in a pot of salted water according to package directions. Drain and rinse with cold water to stop cooking. Drain and set aside.
In a large liquid measuring cup, combine almond butter, rice vinegar, soy sauce and sesame oil. Stir to combine. Let sit for a couple minutes to allow almond butter to dissolve.
**If sauce is too thick, add 1 Tbsp water to thin out slightly.
Once sauce is smooth, pour over cooked spaghetti noodles. Toss to combine. Serve with chopped green onions, toasted sesame seeds, and crushed red pepper flakes. Enjoy warm or chilled.