Preheat the oven to 450°F/230°C or heat the grill
Prick the eggplant in several places.
I put the vegetables directly on the oven rack, but you can put them on cookie sheets.
If you want to roast the garlic, cut the top of a garlic bulb off to expose the cloves and drizzle with some olive oil. Wrap the bulb in aluminum foil. It will take about 30 minutes for the cloves to soften. Keep an eye on it so the garlic doesn't burn, and remove it early if necessary. Burnt garlic = very bitter.
Roast the eggplant and peppers for about 30 - 45 minutes. Turn them once or twice while they're roasting.
The vegetables are ready when the skins have blistered and the flesh has softened somewhat. The eggplant will actually collapse a little bit. It's easier to peel the skins if they are blistered but not charred (ask me how I know...)
Remove the vegetables from the oven or grill and cover them with a large towel.
When they are cool enough to handle, cut the eggplant in half and scoop out the flesh. Place it into a large bowl or food processor.
Peel the skin from the peppers and remove the seeds and stems. Add them to the eggplant.
Add the garlic, lemon juice, olive oil and salt and pepper.
Pulse in the food processor or use an immersion blender to mix everything together until it's nice and smooth. Taste and adjust the salt and pepper as needed.