Heat the olive oil in a heavy-based pot over medium heat. Add the onion, garlic and salt, then cook until the onion is translucent, about 4 to 5 minutes.
Add tomato paste and cook, stirring, for 2 minutes. Add sun-dried tomato (with its oil) and the crumbled stock cube. Cook for 3 minutes.
Add canned tomato, water (use water to rinse the cans), sugar and pepper. Bring to a simmer and cook for 25 minutes, or until the tomatoes have broken down. Using a stick blender, blend the soup until smooth.
Ladle into bowls. Top with extra sun-dried tomatoes, if using, and drizzle with olive oil. Serve with croutons on the side for dunking.
Crostini: Preheat oven to 180C fan-forced (200C conventional). Brush both sides of the bread with olive oil, and sprinkle with salt. Place bread slices on a baking tray and bake for 8 minutes, turning halfway, until crispy and light golden. Serve with soup.
Note: You can substitute a chicken stock cube for the vegetable stock cube, or you can use vegetable or chicken stock instead of a stock cube and water.
