How to Make It
In a large, deep skillet, heat 1/4 cup of the oil until nearly smoking. Add the squash mix and onion and cook over high heat, stirring, until lightly charred in spots and crisp-tender, about 8 minutes. Add the tomatoes, crushing them lightly with your hands as you add them. Add the crushed red pepper, season with salt and cook over high heat, stirring occasionally, until softened, about 5 minutes. Add the wine and cook until nearly evaporated.
Meanwhile, cook the pasta in a large pot of boiling salted water until al dente. Drain the pasta, reserving 3/4 cup of the cooking water.
Add the pasta to the skillet along with the spinach, ricotta and the reserved cooking water. Toss over moderately high heat until the spinach is wilted and the sauce is thickened and clings to the pasta. Transfer the pasta to a platter and drizzle with the remaining 2 tablespoons of olive oil.
Buckwheat pasta is available online at pastacheese.com.