Add the chopped onion. Cook, stirring often, until tender, about five minutes.
Stir in the garlic and a generous pinch of salt.
Cook, stirring for about 30 seconds to a minute.
Add the tomatoes, sugar, basil sprigs or leaves.
Cook, stirring often, until the tomatoes have cooked down and smell fragrant, 15 to 20 minutes.
Add the water and chicken bouillon.
Bring to a simmer, cover and reduce the heat to low.
Simmer 15 minutes.
Puree in a blender in small batches, taking care to place a towel over the top of the blender and hold it down tightly.
Return to the pot, add pepper to taste and adjust salt.
Serve garnished with slivered basil leaves on top