Keto Roasted Tomato Basil Pesto Pasta with Walnuts
A vibrant twist on classic pesto, this dish combines roasted cherry tomatoes, toasted walnuts, and fresh basil with anchovy umami and bright lemon. The tomatoes add sweetness and acidity while the walnuts replace traditional pine nuts for earthiness. Serve warm as a main course for weeknight dinners or light lunches. This version balances herbaceous basil against caramelized tomato depth, creating a more complex pesto than raw versions.
Ingredients
- 1 cup walnut, whole
- 2 pint cherry tomato, whole
- ⅓ cup olive oil
- ½ teaspoon kosher salt
- 6 anchovy fillet, in oilnonenullvegetarianfish-free
omit entirely or use capers for umami
- 2 clove garlic
- 1 lemon, zest and juice
- ¼ teaspoon crushed red pepper flakes
- ½ ounce Parmesan cheese, grated
- 1 teaspoon black pepper, ground
- 12 ounce spaghetti
- ½ cup fresh basil, leaves
Instructions
- 1
Preheat oven to 350F (350°F).
- 2
Toast walnuts on a rimmed baking sheet in the center of the oven, stirring halfway, until slightly darkened.
- 3
Switch to broiler setting. Toss cherry tomatoes with olive oil and kosher salt on a rimmed baking sheet.
- 4
Place sheet 8-10 inches from broiler heat until tomatoes soften, blister, and release liquid.
- 5
Combine anchovies, lemon juice, garlic, red pepper flakes, and Parmesan in a blender or food processor, pulse until finely ground.
- 6
Add two-thirds of the toasted walnuts and half the roasted tomatoes. Stream in olive oil with motor running until just combined. Season with salt and black pepper.
- 7
Puree for a few seconds until combined, then transfer pesto to a large bowl.
- 8
Cook spaghetti in boiling salted water according to package directions. Reserve 1/2 cup pasta liquid and drain.
- 9
Toss pasta with pesto, adding reserved pasta liquid gradually until sauce coats noodles.
- 10
Top with fresh basil, remaining roasted tomatoes, Parmesan, chopped walnuts, black pepper, and olive oil drizzle.
Tips
Reserve pasta water before draining - the starch helps emulsify the pesto and coat noodles evenly without making the sauce too heavy.
Toast walnuts fully before processing so they release oils and develop nutty flavor. Prevent bitterness by watching closely during the final minutes.
Good to Know
Pesto keeps covered in the refrigerator for up to 5 days. Store separately from cooked pasta. Reheat gently with reserved pasta water to restore sauce consistency.
Make pesto up to 2 days ahead and refrigerate. Toast walnuts and roast tomatoes the same day. Cook pasta just before serving for best texture.
Serve immediately while pasta is hot. Offer extra grated Parmesan, olive oil, and fresh basil on the side for individual customization.
Common Mistakes
Over-blend pesto to avoid a paste texture - pulse in short bursts to maintain flecked consistency and bright color
Don't skip reserving pasta water - without starch emulsion, the sauce won't coat evenly and will seem thin
Avoid charring walnuts past golden brown to prevent acrid, bitter flavors that overpower delicate basil
Substitutions
Dairy-Free Swaps
Nut-Free Alternatives
General Alternatives
omit entirely or use capers for umami
FAQ
Can I make this pesto dairy-free?
Omit Parmesan entirely or substitute with nutritional yeast for a similar savory depth. The dish remains flavorful from anchovy umami and roasted tomatoes, though less sharp overall.
What if I don't have fresh basil?
Use 2 teaspoons dried basil mixed into the pesto during blending, though flavor will be more muted. Add fresh herbs only at the end as garnish if available later.
Can I freeze leftover pesto?
Yes, freeze in ice cube trays for up to 3 months. Thaw in the refrigerator and thin with olive oil or pasta water when reheating. Basil may darken slightly after freezing.