Heat oil in a large stockpot over medium-high heat.
Add leeks, celery and sugar,cook for three minutes,until tender.
Add thyme and cayenne pepper and stir to coat.
Transfer mixture to blender or food processor and add diced tomatoes.
Puree` until smooth; return puree` to stockpot.
Place the pot over high heat, add stock and bring mixture to a boil.
Stir in pasta and cook for three minutes, until pasta is tender.
Remove from heat and stir in basil.
Season to taste with salt and black pepper;ladle soup into bowls and serve