Add sliced onions, butter, minced garlic, thyme, salt, and 1/4 cup of water to the Instant Pot. Seal and cook on high pressure (Manual/Pressure Cook) for 5 minutes. Release the pressure immediately after. Turn on the Saute feature. Using a rubber spatula, continue to mix until the onions start to carmelize—about 3 minutes. Add in the wine, then let it simmer for about 10 minutes, or until the wine cooks through. Pour in the beef broth. Let it simmer for 20 minutes while you prepare the bread. While you wait, preheat the oven to 400 degrees. Cut thick slices of the French baguette, about 2 slices per bowl. Brush the olive oil on both sides of the baguette slices, then place on a baking sheet. Toast in the oven on both sides for 6 minutes, flipping the slices after the first Once removed, set the oven to broil. Ladle the soup into oven save bowls or large ramekins. Add slices of baguette to the tops of each bowl, then a slice of Gruyere cheese. Place the bowls on a clean baking sheet. Carefully place in the oven and broil for 3 to 5 minutes, or until the cheese starts to get bubbly. Be careful when serving, the ramekins will be hot!