In a medium bowl, combine the diced red onion, capers, basil, mustard, sherry vinegar, tamari, salt, pepper and a big splash of extra virgin olive oil. Cut the avocado down the middle and remove the pit. Carefully peel the exterior, trying to preserve the integrity of the flesh. Dice it up somewhat small and toss it into the bowl with the capers, mustard, sherry vinegar, tamari, lime juice, salt, and pepper. etc. Squeeze in the rest of the lime juice. Toss everything to combine, check for seasoning, and adjust accordingly.