1.Dry-fry seeds in a large saucepan over medium heat for 3 minutes or until fragrant. Transfer to a small heatproof bowl.
2.Heat oil in same cleaned pan over medium heat, cook onion and garlic, stirring, 3 minutes or until onion softens. Add capsicum, cook 1 minute. Add paste, tomatoes and the water, bring to the boil. Reduce heat, simmer, uncovered, 25 minutes or until thickened. Season to taste.
3.Meanwhile, cook pasta in a large saucepan of boiling salted water until just tender, drain. Return to the pan to keep warm.
4.Remove sauce from heat, stir in cream and seeds. Using a hand-held blender, blend sauce until smooth (reheat sauce if necessary). Add sauce to pasta with spinach, toss to combine. Season. Serve topped with shaved parmesan, if you like.