To make the aioli, whisk all ingredients in a bowl, cover and refrigerate at least 30 minutes.
Fry the sausage pieces in a large pan til done to your preference, remove from pan and set aside, keep juices in the pan.
Add onion slices, season with salt and saute for about a minute til they begin to soften slightly. Add spinach and continue to saute, tossing frequently, til spinach is wilted.
Cut and butter the bread and toast it in a separate skillet.
Add roasted red pepper slices to the pan of vegetables. Cook another minute just to heat up the peppers.