Step 1
In a small bowl, combine cinnamon, cumin, cayenne and ½ teaspoon salt.
Step 2
Heat a heavy pot (2 to 3 quarts) with a tight-fitting lid over medium until hot but not smoking. Add couscous and toast, stirring often, until golden and fragrant, about 3 minutes. Transfer toasted couscous to a bowl.
Step 3
Add oil to pot and raise heat to medium-high. When it shimmers, add eggplant, onion, ½ teaspoon salt and ¼ teaspoon pepper and cook, stirring often, until onions are softened and golden and the eggplant is browned and slightly shrunken, 8 to 10 minutes. Add garlic and stir just until fragrant.
Step 4
Add tomato paste and the prepared spice mixture and cook, stirring, 1 minute. Stir in toasted couscous, tomato and 1½ cups water, cover, reduce the heat to low and simmer until the couscous has absorbed all the liquid, 8 to 12 minutes. Turn off the heat and let rest 2 minutes. Uncover, stir in paprika and parsley, then taste and adjust the seasoning with salt. Serve immediately and dollop with yogurt, if desired.