Halve onions and slice as thinly as you can. In a heavy bottomed saucepan, heat oil and butter over medium-high heat. Add onions and garlic; stir well to coat. Core and thinly slice pears one at a time, adding to pan immediately to prevent browning.

Sprinkle sugar over mixture and stir until dissolved. Reduce heat to medium and gently simmer, uncovered, for 40–50 minutes, stirring frequently. Reduce heat if mixture begins to scorch or stick. Onions are cooked when all juices have evaporated and they are soft and sticky.

Meanwhile, heat three 1-cup jars and lids.

Add wine, vinegar, and cinnamon stick to onion mixture. Bring to a light boil and keep simmering, stirring frequently, until onions are golden and liquid is reduced by more than half. Marmalade is done when a wooden spoon drawn across pan bottom leaves a path that fills rapidly with thick syrupy juice.

Remove cinnamon stick (or leave in one jar for effect). Fill hot jars, leaving 1/4-inch headspace. Top with lids. Process jars at a full rolling boil for 15 minutes.