Preheat a grill (or grill pan). You want it pretty hot for this recipe.
Clean and trim the portobello mushrooms.
Brush the grill with oil and place the mushrooms top side down. Cook for 5 minutes.
Turn the mushroom 45 degrees and cook for 5 minutes.
Now flip the mushroom over and cook repeating the process above.
Slice onion into 1/2" slices, set aside.
From a can of whole sliced pineapples, pat the liquid dry from the slices. We want them to grill, not steam in their liquid.
Once the mushroom is done, first oil the grill again before proceeding with the onion and pineapple. They take just a few minutes. Keep that heat high.
Take this time to slice the mushroom and coat with barbecue sauce. You can return the slices to the grill pan prior to assembly for warming, but it's rather difficult to slice with the sauce already on.
I plated mine with my Vegan Carrot Slaw made the day before (see the instructions for the link) and vegan-friendly baked beans.
A handful of spinach leaves and a few cherry tomatoes finish off the dish. You could also quickly grill the tomatoes for added flavor.
Give the mushrooms, onions and tomatoes a sprinkle of sea salt.