Heat the olive oil in a saucepan over high heat. When it shimmers, add the garlic cloves and crushed red pepper. Cook until the garlic is browned at the edges. Remove the garlic, and add the eggplant, cooking until it's browned on the edges. Lower the heat to medium-low.
Add all the other ingredients and stir to blend. Add one and a half cups of the reserved tomato juice. Bring to a light boil and lower the heat to a simmer. Cover the saucepan and simmer for 45 minutes, stirring every now and then.
Roughly puree the soup in a food processor, leaving small chunks of eggplant. Return to the saucepan, add the lemon juice, and adjust seasonings. Add a little water or chicken stock if necessary to lighten up the texture.