Preheat the oven to 450 degrees F. Prick eggplants several times with a fork and set on a parchment paperlined baking sheet. Roast 35 to 40 minutes, turning once or twice, until the eggplant is tender and sunken in the middle.
When cool enough to handle, cut eggplants in half lengthwise. Scoop flesh into a bowl. Add garlic, salt and lemon juice and mash with a fork until somewhat smooth (this can also be done in a food processor). Mix in the tahini; cover and refrigerate. When ready to serve, transfer to a serving bowl and garnish with parsley and, if desired, chopped tomatoes. Drizzle with olive oil and serve.