Holy Zohar text. Daily Zohar -350.

Tikkun 21 – 91

Psalms 81:4 “ תִּקְעוּ בַחֹדֶשׁ שׁוֹפָר;    בַּכֵּסֶה, לְיוֹם חַגֵּנוּ ”
“Blow the horn at the new moon, at the full moon for our feast-day”
On the first day of the seventh month we celebrate Rosh Hashanah. The moon is still in the state before the sun/light reveals itself. It is a state of judgment and our opportunity to have blessings as a result of it.

The Zohar says that the food that we prepare on Rosh Hashanah is like the food Isaac asked his son to prepare before he can channel the blessings to him.
Genesis 27:4 “ וַעֲשֵׂה-לִי מַטְעַמִּים כַּאֲשֶׁר אָהַבְתִּי, וְהָבִיאָה לִּי–וְאֹכֵלָה:  בַּעֲבוּר תְּבָרֶכְךָ נַפְשִׁי, בְּטֶרֶם אָמוּת. ”
“and make me savory food, such as I love, and bring it to me, that I may eat; that my soul may bless you before I die.”

The different types of food we eat and the special blessings that we recite on Rosh Hashanah are our tools to transform the judgment to blessings. 14 days after that when we have the full moon of the seventh month, on the holiday of Sukkot we receive the blessings.
The connection of the food on the material level empowers the Shofar that we use on Rosh Hashanah to break the negativity