Add all the ingredients except the butter and the cornflour to a blender.
Blend until smooth and creamy, scraping down as necessary.
Heat a pot over medium-low heat and add the butter. Let it melt then add the 3 tablespoons of flour. Stir to mix and let cook for 3–4 minutes until the flour is lightly toasted and a shade darker.
Slowly stream in the roasted pepper cream, whisking as you pour so it doesn't clump up. Add the black pepper and whisk while the cream comes to a simmer. Let simmer until thickened, about 3–5 minutes, then remove from heat.
Cook your chosen pasta as indicated in the package.
Serve the pasta with the roasted pepper cream.
Store the roasted pepper cream in the fridge for up to a week.