Step 1

In a small bowl, cover the capers with water and let soak for 15 minutes; drain.

Step 2

Meanwhile, in a large skillet, heat 3 tablespoons of the olive oil. Add the eggplant and cook over moderately high heat until the bottom browns, 5 minutes. Stir and cook until browned all over, 10 minutes longer. Transfer the eggplant to a bowl.

Step 3

Add the remaining 1 tablespoon of olive oil, the onion and celery to the skillet. Cover and cook over low heat, stirring occasionally, for 10 minutes. Add the tomato, cover and cook until soft, about 5 minutes.

Step 4

In a saucepan, simmer the vinegar and sugar to dissolve the sugar. Add the pine nuts and capers and cook for 1 minute.

Step 5

Return the eggplant to the skillet. Stir in the vinegar mixture and cook over low heat for 3 minutes. Season with salt and pepper and transfer to a bowl. Let cool to room temperature, then fold in the avocado.