Soak cashews with boiling water for at least 30 mins.

In a food processor or blender, blend the cashews with half the water that the cashews were soaking in. Blend for about 2 minutes or until it looks like a paste.

Add the rest of the water 1/4 cup at a time, and salt and blend till you get a silky consistency and set aside.

Cook pasta al dente according to the instructions on the package with salted water.

While the pasta water is boiling, melt 2 TBSP of butter in a large skillet on medium-high heat.

Add onions and occasionally stir for about 10 minutes until the onions are browning.

Add garlic and stir for 1 minute.

Stir in the tomatoes and pour in the cashew sauce and pasta water.

Add salt, pepper, and dried oregano, then bring to a quick boil.

Turn off the stove, immediately add the pasta straight from the pot, toss in the remaining 1 TBSP of butter and add the chopped spinach. Stir till all the sauce covers the pasta.

Optional: Garnish with basil and pine nuts!