Dice the onion. Heat a large pot over medium low heat. Add butter. When melted add in onion and garlic. Saute for about 3-4 minutes. Add tomato paste and continue sautéing for about 2 minutes.
Add in tomatoes and roughly chopped basil. Continue stirring together for about 2-3 minutes.
Add in chicken broth, parmesan cheese, and peppercorns. Season with salt. Simmer on medium heat for about 5 minutes until it starts to boil. Then lower heat and cover for about 30 minutes.
When done use an immersion blender to blend it all together. Mix in heavy cream.