Brush the mushrooms carefully with a paper towel to get rid of the excess dirt. Using a spoon, carefully scrape out the gills from the underside of the portobello cap.
Slice the mushroom in half along the perimeter (like you are butterflying it) so you have 2 thin rounds and place them in a large bowl.
In a saute pan add the oil and place over medium heat. When the oil is shimmering, add the garlic and the shallot and cook for no more than 2 minutes. Turn off the heat and add the lemon zest, lemon juice, oregano, thyme, honey, salt, and pepper and whisk vigorously.
Pour the mixture over the mushrooms and with your hands toss gently to coat, making sure there is even coverage.
Let the mushrooms stand at room temperature for at least 45 minutes.
