In a small mason jar, combine the sugar, vinegar, chili sauce, lemon juice and grated onion. Stir to dissolve the sugar and blend ingredients.
Add the canola oil, screw the lid on tight and shake vigorously to bring the dressing together. Give it a taste and season with salt and freshly ground black pepper.
To assemble the salad, place 3-4 butter lettuce leave in the center of a plate to create a "bed" for the other ingredients. Arrange the citrus, avocado, red onion and stilton on top of the butter lettuce.
Give the dressing one more shake and drizzle lightly over the salads. Enjoy!