Dice the aubergines, zucchini, bell peppers and onions into small, equal pieces.
Toss the aubergines, zucchini and bell peppers in extra virgin olive oil. Season with salt and pepper.
Spread the oiled and seasoned vegetables on a single layer in a baking pan. Roast in a pre-heated 250°C / 475°F oven for 35 minutes.
After the vegetables are roasted, heat extra virgin olive oil in a skillet under medium low heat. Saute the minced garlic for a minute until fragrant.
Add the ground cumin and turmeric and let the flavors bloom, around one minute. Stir periodically to prevent the spices from burning.
Add the tomato paste. Cook for two minutes, stirring periodically, to remove the faint metallic aftertaste.
Mix in the roasted vegetables plus the diced red onions. Toss lightly until the tomato paste is fully incorporated. Adjust for seasoning as needed.