Add 1 cup water, ⅔ cup raw cashews, 1 2-ounce jar pimentos, ½ cup nutritional yeast flakes, 2 tablespoons fresh lemon juice, 1 teaspoon salt, ½ teaspoon onion powder, 1 teaspoon garlic powder, 1 teaspoon paprika, ½ teaspoon cumin, and 1 teaspoon cayenne powder (optional) to high-speed blender.
Blend ingredients together until completely smooth.
If blender does not heat mixture, transfer mixture to medium saucepan and place saucepan on stovetop over medium-low heat.
Heat sauce, whisking constantly, until warmed through.
When sauce is hot, transfer sauce to serving bowl. Serve as desired.