Heat the butter in a saucepan over medium-high
heat; cook and stir the yellow and red onion,
shallots, garlic, tomato, carrots, and mushrooms
until the onions are translucent and the carrots
have softened, 10 to 15 minutes. Pour in the beef
broth and 1 cup of Merlot, and bring to a boil,
scraping and dissolving any browned bits of flavor
from the bottom of the pan. Reduce heat, and
simmer until the vegetables are very soft and the
pan juices have reduced by half, about 20 minutes.
Strain out and discard the vegetables from the
sauce. Return the sauce to a boil over medium-high
heat, stir in 1/4 cup of Merlot wine, and reduce
heat. Simmer the sauce until it is reduced to 1/4
of its original volume, stirring occasionally,
about 20 minutes.