Observation by my friends Tom and Joy. I have posted it on iNat in hopes of confirming my tenative ID.

Brown, soft balls growing on sagebrush Artemesia tridentata. I originally thought this to be some sort of fungi but they are not.

Based on the article "Artemisia tridentata and Rhopalomyia medusa" by Daniel Mosquin of UBC on February 3, 2011, I believe that the brown growth are galls induced by Rhopalomyia medusa or some other closely related species. The fact that the galls appear hairless let's me suggest this down to the species.
Link to article https://botanyphoto.botanicalgarden.ubc.ca/2011/02/artemisia_tridentata_and_rhopalomyia_medusa/

"This midge [Rhopalomyia] induces globular, leafy-pubescent, polythalamous [many-chambered] galls on the bud of Great Basin sagebrush (Artemisia tridentata)."
Source :Ron Russo, " Field Guide to Plant Galls of California and Other Western States" as quoted in Mosquin, 2011 article.

The insect induces the plant to grow these galls. In a comment, Daiel Mosquin provides some insight into how this process may occur in reponse to this question:
"Does anybody know the molecular mechanism of transformation of host tissue into gall tissue growth? (e.g. do the parasitic insects inject plasmid DNA?)"

"...you may interested to try to locate Biology of Insect-Induced Galls, edited by J.D. Shorthouse and O. Rohfritsch, Oxford University Press, 1992 (found via Wayne Armstrong’s excellent plant site, in this case, To Be Or Not To Be A Gall, specifically Initiation Of Insect Galls).
And to quote:
“According to K. Hori (Biology of Insect-Induced Galls, Chapter 10, 1992), salivary fluids of hemipterans (bugs) and homopterans (aphids) may include amino acids, auxins (IAA) and various plant digesting enzymes such as pectinases, cellulases and proteases. The precise mechanism by which these chemicals induce cell division and morphogenesis is very complicated and varies with different species and even with different types of plant tissue. An increased concentration of certain plant hormones in the gall tissue may also be important for the morphogenesis of some galls.”