Preheat your oven to 400°F. Get it nice and hot—this matters for proper roasting.
In a 9x13 baking dish or large baking tray, combine the quartered tomatoes, onion, garlic cloves, and carrot. Don't worry about perfect cuts; rough chopping is your friend here.
Toss everything with harissa powder, sea salt, and olive oil. Make sure the vegetables are evenly coated. This step is crucial—you want that harissa powder distributed throughout.
Roast for 60-75 minutes until the vegetables are completely fork-tender and caramelized at the edges. The longer you go (within reason), the deeper the flavor. Your kitchen will smell absolutely incredible.
Transfer the roasted vegetables to a blender along with the vegetable broth. Blend until completely smooth. FYI, if you've got an immersion (stick) blender, you can do this directly in your pot to save dishes.
Pour the blended soup into a medium-sized pot and bring it to a boil over medium-high heat.
Add the date syrup or maple syrup and simmer for 10-15 minutes. This allows the flavors to meld and the soup to reach its full potential.
Taste and adjust seasonings as needed. Add more salt, harissa, or syrup based on your preferences.
Top with fresh parsley before serving for a pop of color and freshness.