In a small mixing bowl, mix together cinnamon, coriander, all spice, cayenne, salt, pepper, thyme, garlic, ginger, lime juice, tamari, coconut sugar, coconut oil, green onions or scallions, and serrano / habanero pepper.
Taste and adjust flavor as needed, adding more tamari for saltiness, lime juice for acidity, fresh herbs for earthy flavor, coconut sugar for sweetness, pepper for heat, or garlic for zing.
Slice eggplant vertically (lengthwise) into 1/2-inch-thick “steaks” and generously brush both sides with the marinade.
Heat up a grill or grill pan to medium-high heat and lightly oil / grease to discourage the eggplant from sticking. Once hot, add eggplant and grill on both sides until golden brown and grill marks are present – about 3-5 minutes each side.
In the meantime, prepare sauce (optional!) by adding BBQ sauce, lime juice, oil, coconut sugar / maple syrup, ginger, salt, pepper, onion, and cayenne pepper to a small and whisking to combine. Taste and adjust flavor as needed, adding more lime for acidity, coconut sugar for sweetness, cayenne for heat, or salt for saltiness.