Spaghetti all'assassina

Name: Spaghetti all'assassina
Cuisine: European, Italian, Mediterranean
Ingredients: 200g 7 oz spaghetti; 1/2 tube tomato concentrate aka paste (or 65g/2-1/2 oz); 50ml 1/8 cup passata di pomodoro aka tomato purée; 1 liter 1 quart water; salt (to taste); 1-2 cloves garlic, finely minced; 1-2 red hot pepper, (preferably fresh, finely minced (or a pinch of red pepper flakes)); 125ml 1/2 cup passata di pomodoro aka tomato purée; olive oil