In a pot with water, boil the guavas for about 6 minutes. Then blend until smooth.
Meanwhile, put the oats in the milk so they can rehydrate about 5 minutes; add a pinch of salt.
Bring the milk-oat mixture to a boil, add the cinnamon stick.
Add the guava puree—but pass it through a sieve or strainer so no seeds get through. (Pro tip: if you don’t, the milk can separate or “cut” — trust me, I learned the hard way.)
Stir in the brown sugar or sweetener of choice.
Let the oatmeal simmer for about 8 minutes (or longer/shorter depending on the thickness you like).
Serve warm or cold (yes, cold is also delicious). Top with the pecans if you like for a little crunch.