Barcelona might be as generously supplied with sushi joints as any other cosmopolitan city, but “fusion” cuisine of any kind is still regarded there with great suspicion. Witness the uproar that ensued when Juanito, the legendary proprietor of Bar Pinotxo in the Boqueria market, introduced a toasted canapé topped with an avocado spread on his menu. How could a place as iconically Catalan as Pinotxo dare to spread a tostada with a Mexican guacamole, the traditionalists cried out. Could this be the end of Catalan cuisine? None of it seemed to bother Juanito, who proudly plied regulars with his new concoction. Besides, his lemony avocado spread, bolstered with sherry vinegar, isn’t exactly guacamole. Juanito serves it on long slices of toasted bread, topped with fat anchovies and sprinkled with chopped, briny black olives.