Caramelized onion and goat cheese tart

There is an old Russian ¹ joke: A woman goes to visit her mother for 2 weeks. When she returns home, her husband looks terrible - gaunt, unshaven, with bags under his eyes. The wife asks: "What happened to you?!" 
The husband replies: "I haven't eaten anything in 10 days! I am starving, and haven't been able to sleep or concentrate on anything."
Wife: "How is that possible? I left a refrigerator full of groceries, enough food for a month, and really detailed recipe cards."
Husband: "I know! I was fine following the recipe cards for 3 days, but after that I was stuck. All the recipes start with take a clean pan."
~ Folk humor, translated by the hedgehog

The first step in making a caramelized onion tart, or, for that matter, any recipe that requires caramelized onions, is to prepare the onions. The process is very simple, and does not require a lot of attention, although it will take a few hours. This is a perfect activity if you are planning to spend a few hours watching Netflix, reading or doing chores around the house mindlessly wandering online. 

• add sweetness and crunch to sandwiches
• top pizzas, including that great French classic - pissaladière
• be tossed with green beans or pasta
• get baked into caramelized onion and gruyere biscuits
• achieve the glory that is French onion soup
• get eaten with a fork directly from the jar 

Since the effort required for a bigger batch is marginal, make a large pot and freeze whatever remains after a few days. The best way to freeze the onions is to put them into a Ziplock bag, squeeze out all the air, close the bag and distribute the onions in an even layer. Once frozen ², simply break off the portion needed for a recipe. 

So, take a clean pot...