Add the sun-dried tomatoes, spinach, basil, sunflower seeds, garlic, salt and pepper to the bowl of a food processor. Pulse until finely chopped.
With the food processor running, slowly pour in the olive oil and vinegar. Process until mostly smooth, scraping down the sides of the bowl as needed.
To thin out the pesto, add in additional olive oil a little at a time.
Notes
If you are using sun-dried tomatoes packed in oil, you can use that oil in place of some/all of the olive oil. If your sun-dried tomatoes do not come packed in oil, soak them in hot water until tender before using in the recipe.
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