Cook pasta in plenty of lightly salted boiling water until al dente, following package instructions. Drain, rinse under cold running water and leave to cool. Trim asparagus and cut into small pieces. Place in a steamer basket. Fill a large saucepan with water to a depth equal to the width of two fingers; bring to a boil. Reduce heat to a simmer. Place steamer basket on top of pan. Cover; cook asparagus 6 to 8 minutes. Leave to cool.
Slice zucchini into rounds. Cut capsicum in half and chop into small pieces. Separate tuna into flakes with a fork. Finely chop olives.
To make herb vinaigrette, whisk all the ingredients in a large bowl until combined. Add pasta, asparagus, zucchini, capsicum and olives.
To make aioli, have all ingredients at room temperature to avoid curdling. Grind garlic and salt to a fine paste in a bowl. Using electric beaters or a whisk, beat in egg yolk and 1/2 tablespoon vinegar until creamy. Add oil, drop by drop at first, then in a steady stream. Beat until mixture is thick and creamy. Season well with remaining 1/2 tablespoon vinegar, lemon juice and salt and pepper to taste.
Distribute salad among serving bowls and add tuna. Spoon a little aioli on top. Serve remainder on the side.