There are several species of the genus Acmispon, and they are difficult to distinguish. I’m taking a wild guess that this is the Acmispon glaber, otherwise known as Common Deerweed, California Broom or Western Birds-Foot Trefoil.
Found in dry areas of CA, it blooms from March to August. Its flowers are tiny, 7-11 mm, yellow and clustered together. They become reddish with age. The A. glaber food is consumed by hummingbirds, bees, butterfly and deer. In sufficient amount, it is a habitat and shelter for the world’s rarest butterfly, the Palos Verdes Blue, found only in southwest LA County. These A. glabers were found in Santa Cruz Mountains.
Whatever they are, they sure are pretty, and you got such a beautiful photo of them.